Ninja: Detect MSVC /showIncludes prefix with compiler flags (#15596)
Move detection over to the compiler id logic where we have already constructed the list of compiler flags from ARG1 and CMAKE_<LANG>_FLAGS. Pass the flags when we execute "cl" with "/showIncludes". Also pass "/c" because we only need to compile, not link. Check the compiler process exit code before trusting its output.
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