bootstrap/install.rs: support a nonexistent prefix in x.py install

[nodakai]

PR #49778 introduced fs::canonicalize() which fails for a nonexistent path.
This is a surprise for someone used to GNU Autotools' configure which can create any necessary intermediate directories in prefix.

This change makes it run fs::create_dir_all() before canonicalize().

[rust-highfive]

r? @Mark-Simulacrum

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[rust-highfive]

The job mingw-check of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

##[section]Starting: Linux mingw-check
##[section]Starting: Initialize job
Agent name: 'Azure Pipelines 4'
Agent machine name: 'fv-az645'
Current agent version: '2.170.1'
##[group]Operating System
16.04.6
LTS
LTS
##[endgroup]
##[group]Virtual Environment
Environment: ubuntu-16.04
Version: 20200604.1
Included Software: https://github.com/actions/virtual-environments/blob/ubuntu16/20200604.1/images/linux/Ubuntu1604-README.md
##[endgroup]
Agent running as: 'vsts'
Prepare build directory.
Set build variables.
Download all required tasks.
Download all required tasks.
Downloading task: Bash (3.163.3)
Checking job knob settings.
   Knob: AgentToolsDirectory = /opt/hostedtoolcache Source: ${AGENT_TOOLSDIRECTORY} 
   Knob: AgentPerflog = /home/vsts/perflog Source: ${VSTS_AGENT_PERFLOG} 
Start tracking orphan processes.
##[section]Finishing: Initialize job
##[section]Starting: Configure Job Name
==============================================================================
---
========================== Starting Command Output ===========================
[command]/bin/bash --noprofile --norc /home/vsts/work/_temp/0b3cd52f-1b22-40b4-8374-ec2062b96d67.sh

##[section]Finishing: Disable git automatic line ending conversion
##[section]Starting: Checkout rust-lang/rust@refs/pull/73350/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
---
##[command]git remote add origin https://github.com/rust-lang/rust
##[command]git config gc.auto 0
##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
##[command]git config --get-all http.proxy
##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/73350/merge:refs/remotes/pull/73350/merge
---
 ---> f883e675ad62
Step 6/7 : ENV RUN_CHECK_WITH_PARALLEL_QUERIES 1
 ---> Using cache
 ---> c0b156eb069c
Step 7/7 : ENV SCRIPT python3 ../x.py test src/tools/expand-yaml-anchors &&            python3 ../x.py check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu &&            python3 ../x.py build --stage 0 src/tools/build-manifest &&            python3 ../x.py test --stage 0 src/tools/compiletest &&            python3 ../x.py test src/tools/tidy &&            python3 ../x.py doc --stage 0 src/libstd &&            /scripts/validate-toolstate.sh
 ---> 8541bab6b38c
Successfully built 8541bab6b38c
Successfully tagged rust-ci:latest
Built container sha256:8541bab6b38c07f1b7eb787539b9cbe93daa6ac4458d3d7bd8a8921622a14ba1
---
    Checking chalk-rust-ir v0.10.0
    Checking rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
    Checking rustc_hir v0.0.0 (/checkout/src/librustc_hir)
    Checking rustc_session v0.0.0 (/checkout/src/librustc_session)
    Checking rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
    Checking rustc_parse v0.0.0 (/checkout/src/librustc_parse)
    Checking rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
    Checking rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
    Checking rustc_ast_passes v0.0.0 (/checkout/src/librustc_ast_passes)
---
configure: rust.debug-assertions := True
configure: llvm.ccache          := sccache
configure: build.submodules     := False
configure: dist.missing-tools   := True
configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
configure: writing `config.toml` in current directory
configure: 
configure: run `python /checkout/x.py --help`
configure: 
---
Hugepagesize:       2048 kB
DirectMap4k:      145344 kB
DirectMap2M:     4048896 kB
DirectMap1G:     5242880 kB
+ python3 ../x.py test src/tools/expand-yaml-anchors
Ensuring the YAML anchors in the GitHub Actions config were expanded
Ensuring the YAML anchors in the GitHub Actions config were expanded
Building stage0 tool expand-yaml-anchors (x86_64-unknown-linux-gnu)
   Compiling unicode-xid v0.2.0
   Compiling syn v1.0.11
   Compiling linked-hash-map v0.5.2
   Compiling lazy_static v1.4.0
   Compiling lazy_static v1.4.0
   Compiling yaml-rust v0.4.3
   Compiling quote v1.0.2
   Compiling thiserror-impl v1.0.5
   Compiling thiserror v1.0.5
   Compiling yaml-merge-keys v0.4.0
   Compiling expand-yaml-anchors v0.1.0 (/checkout/src/tools/expand-yaml-anchors)
Build completed successfully in 0:00:28
+ python3 ../x.py check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu
    Finished dev [unoptimized] target(s) in 0.18s
Checking rustdoc artifacts (x86_64-unknown-linux-gnu -> i686-pc-windows-gnu)
---
    Checking chalk-rust-ir v0.10.0
    Checking rustc_ast_pretty v0.0.0 (/checkout/src/librustc_ast_pretty)
    Checking rustc_hir v0.0.0 (/checkout/src/librustc_hir)
    Checking rustc_session v0.0.0 (/checkout/src/librustc_session)
    Checking rustc_query_system v0.0.0 (/checkout/src/librustc_query_system)
    Checking rustc_parse v0.0.0 (/checkout/src/librustc_parse)
    Checking rustc_hir_pretty v0.0.0 (/checkout/src/librustc_hir_pretty)
    Checking rustc_ast_lowering v0.0.0 (/checkout/src/librustc_ast_lowering)
    Checking rustc_ast_passes v0.0.0 (/checkout/src/librustc_ast_passes)
---
skip untracked path cpu-usage.csv during rustfmt invocations
skip untracked path src/doc/book/ during rustfmt invocations
skip untracked path src/doc/rust-by-example/ during rustfmt invocations
skip untracked path src/llvm-project/ during rustfmt invocations
Diff in /checkout/src/bootstrap/install.rs at line 70:
     let libdir_default = PathBuf::from("lib");
     let mandir_default = datadir_default.join("man");
     let prefix = builder.config.prefix.as_ref().map_or(prefix_default, |p| {
-        fs::create_dir_all(p).unwrap_or_else(|err| panic!("could not create {}: {}", p.display(), err));
-        fs::canonicalize(p).unwrap_or_else(|err| panic!("could not canonicalize {}: {}", p.display(), err))
+        fs::create_dir_all(p)
+            .unwrap_or_else(|err| panic!("could not create {}: {}", p.display(), err));
+        fs::canonicalize(p)
+            .unwrap_or_else(|err| panic!("could not canonicalize {}: {}", p.display(), err))
     });
     let sysconfdir = builder.config.sysconfdir.as_ref().unwrap_or(&sysconfdir_default);
     let datadir = builder.config.datadir.as_ref().unwrap_or(&datadir_default);
Running `"/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustfmt" "--config-path" "/checkout" "--edition" "2018" "--unstable-features" "--skip-children" "--check" "/checkout/src/bootstrap/install.rs"` failed.
If you're running `tidy`, try again with `--bless`. Or, if you just want to format code, run `./x.py fmt` instead.
Build completed unsuccessfully in 0:00:34
== clock drift check ==
  local time: Sun Jun 14 18:37:09 UTC 2020
  network time: Sun, 14 Jun 2020 18:37:09 GMT
  network time: Sun, 14 Jun 2020 18:37:09 GMT
== end clock drift check ==

##[error]Bash exited with code '1'.
##[section]Finishing: Run build
##[section]Starting: Checkout rust-lang/rust@refs/pull/73350/merge to s
Task         : Get sources
Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
Version      : 1.0.0
Author       : Microsoft
Author       : Microsoft
Help         : [More Information](https://go.microsoft.com/fwlink/?LinkId=798199)
==============================================================================
Cleaning any cached credential from repository: rust-lang/rust (GitHub)
##[section]Finishing: Checkout rust-lang/rust@refs/pull/73350/merge to s
Cleaning up task key
Start cleaning up orphan processes.
Terminate orphan process: pid (3480) (python)
##[section]Finishing: Finalize Job

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[Mark-Simulacrum]

Seems reasonable. @bors r+

[bors]

📌 Commit 8e7606f has been approved by Mark-Simulacrum

[RalfJung]

@bors rollup