tests: Add '%clangxx' substitution, for 'clang++'

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@96510 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/lit.cfg b/test/lit.cfg
index 4d7a17a..5b18687 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -123,12 +123,15 @@
 if not lit.quiet:
     lit.note('using clang: %r' % config.clang)
 config.substitutions.append( ('%clang_cc1', config.clang + ' -cc1') )
+config.substitutions.append( ('%clangxx', ' ' + config.clang + '++ ') )
 config.substitutions.append( ('%clang', ' ' + config.clang + ' ') )
 
 # FIXME: Find nicer way to prohibit this.
 config.substitutions.append(
     (' clang ', """*** Do not use 'clang' in tests, use '%clang'. ***""") )
 config.substitutions.append(
+    (' clang++ ', """*** Do not use 'clang++' in tests, use '%clangxx'. ***"""))
+config.substitutions.append(
     (' clang-cc ',
      """*** Do not use 'clang-cc' in tests, use '%clang_cc1'. ***""") )
 config.substitutions.append(