[lit] Pass LLVM_PROFILE_FILE environment

[thieta]

Summary

When building a PGO version of LLVM you might want to customize
the output profile file when building tests. For this to work
we need to pass LLVM_PROFILE_FILE enviroment.

[thieta]

Thanks!

llvm/utils/lit/lit/TestingConfig.py

def fromdefaults(litConfig):
             'LIBRARY_PATH',
             'LD_LIBRARY_PATH',
             'SYSTEMROOT',
             'TERM',
             'CLANG',
             'LLDB',
             'LD_PRELOAD',
             'LLVM_SYMBOLIZER_PATH',
+            'LLVM_PROFILE_FILE',
             'ASAN_SYMBOLIZER_PATH',
             'HWASAN_SYMBOLIZER_PATH',
             'LSAN_SYMBOLIZER_PATH',
             'MSAN_SYMBOLIZER_PATH',
             'TSAN_SYMBOLIZER_PATH',
             'UBSAN_SYMBOLIZER_PATH',
             'ASAN_OPTIONS',
             'LSAN_OPTIONS',