Tell CMake not to check for a C++ compiler.

Tell CMake not to check for a C++ compiler.

We only need a C compiler, and if either

1) the C and C++ compilers don't match (e.g., a defaults-to-64-bit GCC
and a defaults-to-32-bit Oracle Studio C++)

or

2) you set CFLAGS in the environment to force a 64-bit build but don't
also set CXXFLAGS

CMake will get confused and think it's doing a 32-bit build even though
we'll be doing a 64-bit build, and all sorts of weirdness will occur.

Just say "C" in the project() command.

(cherry picked from commit 3834579486f1bb4a002e45ceb6c015cd28b84611)