llvm-config --cflags --cxxflags --cppflags

We shouldn't impose those flags on people who use llvm-config for
building their own projects.

llvm-svn: 124399

of compiler parameters explicitly added by the build
specification. This macro replaces the cmake built-in
`add_definitions'.

Detects glibc and defines _GNU_SOURCE accordingly.

Resolves bug 3882.

llvm-svn: 68428