[CMake] Support compiler-rt builtins library in tests
[CMake] Support compiler-rt builtins library in tests

We're building tests with -nostdlib which means that we need to
explicitly include the builtins library. When using libgcc (default)
we can simply include -lgcc_s on the link line, but when using
compiler-rt builtins we need a complete path to the builtins library.

This path is already available in CMake as <PROJECT>_BUILTINS_LIBRARY,
so we just need to pass that path to lit and if config.compiler_rt is
true, link it to the test.

Prior to this patch, running tests when compiler-rt is being used as
the builtins library was broken as all tests would fail to link, but
with this change running tests when compiler-rt bultins library is
being used should be supported.

Differential Revision: https://reviews.llvm.org/D56701

git-svn-id: 62ef012455b6b8fcec9c41ca270ebf409aae1006@353208 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libunwind,llvm-mirror/libunwind,llvm-mirror/libunwind