Make profiler_builtins an optional dependency of sysroot, not std

This avoids unnecessary rebuilds of std (and the compiler) when
`build.profiler` is toggled off or on.

Author: Zalathar

library/Cargo.lock

@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "addr2line"
@@ -340,7 +340,6 @@ dependencies = [
  "object",
  "panic_abort",
  "panic_unwind",
- "profiler_builtins",
  "r-efi",
  "r-efi-alloc",
  "rand",
@@ -368,6 +367,7 @@ name = "sysroot"
 version = "0.0.0"
 dependencies = [
  "proc_macro",
+ "profiler_builtins",
  "std",
  "test",
 ]

library/std/Cargo.toml

@@ -18,7 +18,6 @@ panic_unwind = { path = "../panic_unwind", optional = true }
 panic_abort = { path = "../panic_abort" }
 core = { path = "../core", public = true }
 compiler_builtins = { version = "0.1.133" }
-profiler_builtins = { path = "../profiler_builtins", optional = true }
 unwind = { path = "../unwind" }
 hashbrown = { version = "0.15", default-features = false, features = [
     'rustc-dep-of-std',
@@ -98,7 +97,6 @@ backtrace = [
 ]
 
 panic-unwind = ["panic_unwind"]
-profiler = ["profiler_builtins"]
 compiler-builtins-c = ["alloc/compiler-builtins-c"]
 compiler-builtins-mem = ["alloc/compiler-builtins-mem"]
 compiler-builtins-no-asm = ["alloc/compiler-builtins-no-asm"]

library/sysroot/Cargo.toml

@@ -6,6 +6,7 @@ edition = "2021"
 # this is a dummy crate to ensure that all required crates appear in the sysroot
 [dependencies]
 proc_macro = { path = "../proc_macro" }
+profiler_builtins = { path = "../profiler_builtins", optional = true }
 std = { path = "../std" }
 test = { path = "../test" }
 
@@ -23,7 +24,7 @@ system-llvm-libunwind = ["std/system-llvm-libunwind"]
 panic-unwind = ["std/panic_unwind"]
 panic_immediate_abort = ["std/panic_immediate_abort"]
 optimize_for_size = ["std/optimize_for_size"]
-profiler = ["std/profiler"]
+profiler = ["dep:profiler_builtins"]
 std_detect_file_io = ["std/std_detect_file_io"]
 std_detect_dlsym_getauxval = ["std/std_detect_dlsym_getauxval"]
 std_detect_env_override = ["std/std_detect_env_override"]