Reland "[lit] Adding config initialization to lit tests in clang-tools-extra"

Adding the config initialization to clang-tools-extra so that tests that
use REQUIRES, UNSUPPORTED, and XFAIL based on platform or target triple
work properly.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@328131 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/lit.site.cfg.in b/test/lit.site.cfg.in
index 86e9617..948e469 100644
--- a/test/lit.site.cfg.in
+++ b/test/lit.site.cfg.in
@@ -23,5 +23,7 @@
     key, = e.args
     lit_config.fatal("unable to find %r parameter, use '--param=%s=VALUE'" % (key,key))
 
+@LIT_SITE_CFG_IN_FOOTER@
+
 # Let the main config do the real work.
 lit_config.load_config(config, "@CLANG_TOOLS_SOURCE_DIR@/test/lit.cfg")