Appease the buildbots with the special case for non-set variables

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@219994 91177308-0d34-0410-b5e6-96231b3b80d8

test/lit.cfg

@@ -271,8 +271,9 @@ config.substitutions.append( ('%clangxx', ' ' + config.clang +
 config.substitutions.append( ('%clang', ' ' + config.clang + ' ') )
 config.substitutions.append( ('%test_debuginfo', ' ' + config.llvm_src_root + '/utils/test_debuginfo.pl ') )
 config.substitutions.append( ('%itanium_abi_triple', makeItaniumABITriple(config.target_triple)) )
-config.substitutions.append( ('%itanium_abi_host_triple', makeItaniumABITriple(config.host_triple)) )
 config.substitutions.append( ('%ms_abi_triple', makeMSABITriple(config.target_triple)) )
+if config.host_triple != '@LLVM_HOST_TRIPLE@':
+  config.substitutions.append( ('%itanium_abi_host_triple', makeItaniumABITriple(config.host_triple)) )
 
 # FIXME: Find nicer way to prohibit this.
 config.substitutions.append(