llvm-svn: 93817

Add a VISIBILITY_HIDDEN option, which can be used to make all compiler-rt function definitions hidden/private extern.

llvm-svn: 93790

llvm-svn: 93721

libraries to generate.
 - Each library may be built with different flags and for different
   architectures, and there is support for building Darwin style fat archives.

 - Uses an ambituous amount of make programming, but should be hidden to
   users and developers.

llvm-svn: 93720