Bootc status fix

[Johan-Liebert1]

For BLS complaint bootloaders, just systemd for now, we were still
looking for entries in boot/loader/entries which was failing as
entries for these bootloaders will be stored in the ESP.

Also, refactor to use TempMount::mount_dev for mounting ESP

[gemini-code-assist]

Code Review

This pull request correctly fixes an issue with locating boot entries for systemd-boot by mounting the ESP. The refactoring to use TempMount for managing the mount lifecycle is a solid improvement for code clarity and safety. I've identified a critical compilation bug related to a use-after-move in the new logic for determining boot entry titles, and a minor issue with discarded error information. I've provided suggestions to address these points. Overall, the changes are well-aligned with the pull request's goal.

[jeckersb]

Generally looks fine to me, just a few minor things inline.

[Johan-Liebert1]

Tests for centos9 seem to be failing with

cargo_build: invalid option -- '-'
error: /builddir/build/originals/bootc.spec: line 94: Unknown option - in cargo_build(naf:)

I can't figure out what the macro actually expands to, but the problem is probably in the following control flow

# Build the main bootc binary
%if 0%{?fedora} || 0%{?rhel} >= 10
    %cargo_build %{?with_rhsm:-f rhsm}
%else
    %cargo_build %{?with_rhsm:--features rhsm}
%endif

[jeckersb]

Hm the macros must have been updated in c9s? I'll look into that, I had to figure out that mess the first time around.

[jeckersb]

Hm the macros must have been updated in c9s? I'll look into that, I had to figure out that mess the first time around.

Yep, that's indeed the case - https://gitlab.com/redhat/centos-stream/rpms/rust/-/commit/54e4b48d95a9fe0d459f464b2a672325673254a8

I'll fix it in a separate PR and then we can just rebase this one.

[jeckersb]

Actually nm, those jobs aren't required, we can just merge this and then fix the macros issue.