[libcxxabi] Pass LIBCXXABI_SYSROOT and LIBCXXABI_GCC_TOOLCHAIN to lit

These are expected to be set by the shared lit scripts used from libc++.

Differential Revision: https://reviews.llvm.org/D40818

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@320445 91177308-0d34-0410-b5e6-96231b3b80d8

test/lit.site.cfg.in

@@ -20,6 +20,8 @@ config.enable_exceptions        = "@LIBCXXABI_ENABLE_EXCEPTIONS@"
 config.host_triple              = "@LLVM_HOST_TRIPLE@"
 config.target_triple            = "@TARGET_TRIPLE@"
 config.use_target               = len("@LIBCXXABI_TARGET_TRIPLE@") > 0
+config.sysroot                  = "@LIBCXXABI_SYSROOT@"
+config.gcc_toolchain            = "@LIBCXXABI_GCC_TOOLCHAIN@"
 config.cxx_ext_threads          = "@LIBCXXABI_BUILD_EXTERNAL_THREAD_LIBRARY@"
 
 # Let the main config do the real work.