This failure mode shows up occasionally when users try to include C headers in
C++ projects or when porting from Windows. We might as well recover in the way
the user expected, thus avoiding confusing diagnostic messages at point of use.
llvm-svn: 209963
- This is designed to make it obvious that %clang_cc1 is a "test variable"
which is substituted. It is '%clang_cc1' instead of '%clang -cc1' because it
can be useful to redefine what gets run as 'clang -cc1' (for example, to set
a default target).
llvm-svn: 91446