Revert "Revert "Reduce CoreCLR PAL""

[janvorli]

Reverts #76860

[janvorli]

@am11 this would not work. The PAL maintains its own copy of the environment, so the CreateProcessW would not see the changes added by the OS putenv.

[janvorli]

@jkotas the _putenv turned out to be the only issue, so I've put it back. Can you please take a look at this revert of revert?
Please note I've left a dummy change in one of the files in the eng so that this PR verifies the mono build. I'll remove it before merging the change.

[jkotas]

LGTM!

[am11]

@janvorli, Mono's llvmaot leg is failing with:

  [ 88%] Building CXX object dlls/mscordbi/utilcode/CMakeFiles/utilcode_obj.dir/configuration.cpp.o
  /__w/1/s/src/mono/dlls/mscordbi/cordb-value.cpp:351:44: error: allocating an object of abstract class type 'CordbArrayValue'
          CordbArrayValue* objectValue = new CordbArrayValue(conn, m_pCordbType, m_debuggerId, m_pClass);
                                             ^
  /__w/1/s/src/coreclr/pal/prebuilt/inc/cordebug.h:15647:43: note: unimplemented pure virtual method 'HasBaseIndicies' in 'CordbArrayValue'
          virtual HRESULT STDMETHODCALLTYPE HasBaseIndicies(
                                            ^
  /__w/1/s/src/coreclr/pal/prebuilt/inc/cordebug.h:15650:43: note: unimplemented pure virtual method 'GetBaseIndicies' in 'CordbArrayValue'
          virtual HRESULT STDMETHODCALLTYPE GetBaseIndicies(
                                            ^
  1 error generated.

https://dev.azure.com/dnceng-public/public/_build/results?buildId=51175&view=logs&jobId=cc858e6b-b6f5-5c08-4b62-8cd383bd096a&j=cc858e6b-b6f5-5c08-4b62-8cd383bd096a&t=74861b75-1f67-5a94-490e-d5eb4723f5a5

Looks like dummy change was needed in src/tests as well.

[janvorli]

@am11 this doesn't seem to be related to my changes. I have not removed anything that could result in this error. And yesterday I've built using the same command line that the failing build is using locally and it passed.

[janvorli]

@jkotas seems like it was caused by your #76966.

[am11]

You are right, it is caused by #76966.

[jkotas]

Ugh. #77002