Missing deactivation leaves `CMAKE_PREFIX_PATH` for every activated environment

[h-vetinari]

I found that we are not cleaning up CMAKE_PREFIX_PATH between environments. This leads to CMAKE_PREFIX_PATH having an entry for every environment that's been activated (if it has the compiler in the run section).

AnacondaRecipes/vs2022-feedstock#6

Originally posted by @ELundby45 in #90 (comment)

[h-vetinari]

Reopening this after #93 got reverted.

[h-vetinari]

This got reverted yet again (in #99, 4f9e21e). I wonder what's causing the issues, e.g. in conda-forge/mimalloc-feedstock#39, which look identical to the problems we had in #94 after #93.

 │ │ -- Check for working C compiler: %BUILD_PREFIX%/Library/bin/clang.exe - broken
 │ │   The C compiler
 │ │     "%BUILD_PREFIX%/Library/bin/clang.exe"
 │ │   is not able to compile a simple test program.
 │ │   It fails with the following output:
 │ │     Change Dir: '%SRC_DIR%/out/release/CMakeFiles/CMakeScratch/TryCompile-0ghiu9'
 │ │     
 │ │     Run Build Command(s): %BUILD_PREFIX%/Library/bin/ninja.exe -v cmTC_1bad2
 │ │     [1/2] %BUILD_PREFIX%\Library\bin\clang.exe   -march=nocona -mtune=haswell -ftree-vectorize -fstack-protector-strong -O2 -ffunction-sections -pipe -D_CRT_SECURE_NO_WARNINGS -nostdlib -fms-runtime-lib=dll -fuse-ld=lld -fno-aligned-allocation  -O0 -g -Xclang -gcodeview -D_DEBUG -D_DLL -D_MT -Xclang --dependent-lib=msvcrtd -MD -MT CMakeFiles/cmTC_1bad2.dir/testCCompiler.c.obj -MF CMakeFiles\cmTC_1bad2.dir\testCCompiler.c.obj.d -o CMakeFiles/cmTC_1bad2.dir/testCCompiler.c.obj -c %SRC_DIR%/out/release/CMakeFiles/CMakeScratch/TryCompile-0ghiu9/testCCompiler.c
 │ │     [2/2] C:\Windows\system32\cmd.exe /C "cd . && %BUILD_PREFIX%\Library\bin\clang.exe -nostartfiles -nostdlib -march=nocona -mtune=haswell -ftree-vectorize -fstack-protector-strong -O2 -ffunction-sections -pipe -D_CRT_SECURE_NO_WARNINGS -nostdlib -fms-runtime-lib=dll -fuse-ld=lld -fno-aligned-allocation  -O0 -g -Xclang -gcodeview -D_DEBUG -D_DLL -D_MT -Xclang --dependent-lib=msvcrtd -nostdlib -Wl,-defaultlib:%BUILD_PREFIX%/lib/clang/19/lib/windows/clang_rt.builtins-x86_64.lib  -Xlinker /subsystem:console -fuse-ld=lld-link CMakeFiles/cmTC_1bad2.dir/testCCompiler.c.obj -o cmTC_1bad2.exe -Xlinker /MANIFEST:EMBED -Xlinker /implib:cmTC_1bad2.lib -Xlinker /pdb:cmTC_1bad2.pdb -Xlinker /version:0.0   -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 -loldnames  && cd ."
 │ │     FAILED: [code=1] cmTC_1bad2.exe 
 │ │ -- Configuring incomplete, errors occurred!
 │ │     C:\Windows\system32\cmd.exe /C "cd . && %BUILD_PREFIX%\Library\bin\clang.exe -nostartfiles -nostdlib -march=nocona -mtune=haswell -ftree-vectorize -fstack-protector-strong -O2 -ffunction-sections -pipe -D_CRT_SECURE_NO_WARNINGS -nostdlib -fms-runtime-lib=dll -fuse-ld=lld -fno-aligned-allocation  -O0 -g -Xclang -gcodeview -D_DEBUG -D_DLL -D_MT -Xclang --dependent-lib=msvcrtd -nostdlib -Wl,-defaultlib:%BUILD_PREFIX%/lib/clang/19/lib/windows/clang_rt.builtins-x86_64.lib  -Xlinker /subsystem:console -fuse-ld=lld-link CMakeFiles/cmTC_1bad2.dir/testCCompiler.c.obj -o cmTC_1bad2.exe -Xlinker /MANIFEST:EMBED -Xlinker /implib:cmTC_1bad2.lib -Xlinker /pdb:cmTC_1bad2.pdb -Xlinker /version:0.0   -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 -loldnames  && cd ."
 │ │     lld-link: error: could not open 'kernel32.lib': no such file or directory
 │ │     lld-link: error: could not open 'user32.lib': no such file or directory
 │ │     lld-link: error: could not open 'gdi32.lib': no such file or directory
 │ │     lld-link: error: could not open 'winspool.lib': no such file or directory
 │ │     lld-link: error: could not open 'shell32.lib': no such file or directory
 │ │     lld-link: error: could not open 'ole32.lib': no such file or directory
 │ │     lld-link: error: could not open 'oleaut32.lib': no such file or directory
 │ │     lld-link: error: could not open 'uuid.lib': no such file or directory
 │ │     lld-link: error: could not open 'comdlg32.lib': no such file or directory
 │ │     lld-link: error: could not open 'advapi32.lib': no such file or directory
 │ │     lld-link: error: could not open 'oldnames.lib': no such file or directory
 │ │     lld-link: error: could not open 'msvcrt.lib': no such file or directory
 │ │     lld-link: error: could not open 'msvcrtd.lib': no such file or directory
 │ │     clang: error: linker command failed with exit code 1 (use -v to see invocation)
 │ │     ninja: build stopped: subcommand failed.

[xhochy]

@h-vetinari I'm not so sure about malloc here, as it had already failed before we merged the change. Let's have a look at other feedstocks.

[h-vetinari]

Well, it looked exactly like #94, so I preferred not breaking other feedstocks again. I'll see if I can try the _27 builds on some feedstock that definitely was previously affected.

[xhochy]

@h-vetinari It's related. It does work again!