build/unittests: Fix llvm-config names for gtest libraries, and bring Makefile
library names in line with those used by CMake.
 - Patch by Johannes Obermayr, with tweaks by me.

llvm-svn: 146706
diff --git a/llvm/utils/unittest/UnitTestMain/Makefile b/llvm/utils/unittest/UnitTestMain/Makefile
index 3082779..7bcb724 100644
--- a/llvm/utils/unittest/UnitTestMain/Makefile
+++ b/llvm/utils/unittest/UnitTestMain/Makefile
@@ -11,7 +11,7 @@
 
 include $(LEVEL)/Makefile.config
 
-LIBRARYNAME = UnitTestMain
+LIBRARYNAME = gtest_main
 BUILD_ARCHIVE = 1
 REQUIRES_RTTI = 1