Move variable only used in an assert into the assert.

This prevents unused variable warnings when building without asserts.

Author: Sterling-Augustine

clang/lib/CodeGen/CoverageMappingGen.cpp

@@ -981,8 +981,8 @@ struct CounterCoverageMappingBuilder
       bool UnnestStart = StartDepth >= EndDepth;
       bool UnnestEnd = EndDepth >= StartDepth;
       if (UnnestEnd) {
-        SourceLocation NestedLoc = getStartOfFileOrMacro(BeforeLoc);
-        assert(SM.isWrittenInSameFile(NestedLoc, BeforeLoc));
+        assert(SM.isWrittenInSameFile(getStartOfFileOrMacro(BeforeLoc),
+                                      BeforeLoc));
 
         BeforeLoc = getIncludeOrExpansionLoc(BeforeLoc);
         assert(BeforeLoc.isValid());