This directory has a variety of .idl files (such as corprof.idl) that need a little special handling when you make changes. Originally when we built on Windows only the build rules would automatically convert the idls into corresponding .h/.c files and include them in compilations. On non-windows platforms we don't have an equivalent for midl.exe which did that conversion so we work around the issue by doing:

• Build on Windows as normal, which will generate files in bin\obj\Windows_NT.x64.Debug\src\inc\idls_out\
• Copy any updated headers into src\pal\prebuilt\inc\
• If needed, adjust any of the .cpp files in src\pal\prebuilt\idl\ by hand, using the corresponding bin\obj\Windows_NT.x64.Debug\src\inc\idls_out*_i.c as a guide. Typically this is just adding MIDL_DEFINE_GUID(...) for any new classes/interfaces that have been added to the idl file.

Include these src changes with the remainder of your work when you submit a PR.