compiling under mingw still need masm because z_Windows_NT-586_asm.asm need masm to build, but can use uasm replace masm.
I have build both x86_64 and i686 versions under mingw without OMPT, and pass all tests.
i686 version have 2 tests need run with administrator privileges.
clang-cl can build, but can not pass tests, because most tests not support clang-cl.
I don't think the if(CMAKE_C_COMPILER_ID STREQUAL "Clang") condition is necessary here.