[MC] Move .cv_loc management logic out of MCContext

MCContext already has many tasks, and separating CodeView out from it is
probably a good idea. The .cv_loc tracking was modelled on the DWARF
tracking which lived directly in MCContext.

Removes the inclusion of MCCodeView.h from MCContext.h, so now there are
only 10 build actions while I hack on CodeView support instead of 265.

llvm-svn: 279847
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 52d7b45..9e5b8c5 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -111,8 +111,9 @@
   if (Insertion.second) {
     // We have to compute the full filepath and emit a .cv_file directive.
     StringRef FullPath = getFullFilepath(F);
-    NextId = OS.EmitCVFileDirective(NextId, FullPath);
-    assert(NextId == FileIdMap.size() && ".cv_file directive failed");
+    bool Success = OS.EmitCVFileDirective(NextId, FullPath);
+    (void)Success;
+    assert(Success && ".cv_file directive failed");
   }
   return Insertion.first->second;
 }