c-index-test/Makefile: Tweak USEDLIBS for cygwin. cygclang.dll is not linked to c-index-test yet.

llvm-svn: 159499
diff --git a/clang/tools/c-index-test/Makefile b/clang/tools/c-index-test/Makefile
index 35f2c04..284844f 100644
--- a/clang/tools/c-index-test/Makefile
+++ b/clang/tools/c-index-test/Makefile
@@ -19,6 +19,7 @@
 
 LINK_COMPONENTS := support mc
 USEDLIBS = clang.a clangFrontend.a clangDriver.a \
+	   clangTooling.a \
 	   clangSerialization.a clangParse.a clangSema.a \
 	   clangAnalysis.a clangEdit.a clangAST.a clangLex.a \
 	   clangBasic.a