`PCbuild/build.bat` does not propagate the PGO test run exit code

[rdesgroppes]

Bug report

Bug description:

If python.bat %pgo_job% fails, the build silently succeeds because %ERRORLEVEL% is reset by subsequent commands inside the same parenthesized block (eager evaluation).

A proposed fix would be to split the block after @echo off, save %ERRORLEVEL% outside the block, and check it after call :Kill.

CPython versions tested on:

3.13, CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-148644: propagate PGO job exit code in PCbuild/build.bat #148645

[zooba]

Historically we've allowed this on purpose, because failing PGO tests haven't necessarily meant that there was a problem in the build, and aborting the build during a release requires a big painful reset that is very disruptive. (And even failing tests still generate a valid profile, which is the whole point.)

These days, we don't use this script for releases anymore, so it seems okay to let it break the build. It's possible that someone is using a custom PGO job and relying on the exit code being ignored, so we won't backport the change.