[Driver] Use -fuse-line-directives by default in MSVC mode

Don't use the GNU extension form of line markers in MSVC mode.

Differential Revision: https://reviews.llvm.org/D46520

llvm-svn: 331666
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index ef76817..6f05fd1 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4215,9 +4215,9 @@
                    IsWindowsMSVC))
     CmdArgs.push_back("-fms-extensions");
 
-  // -fno-use-line-directives is default.
+  // -fno-use-line-directives is default, except for MSVC targets.
   if (Args.hasFlag(options::OPT_fuse_line_directives,
-                   options::OPT_fno_use_line_directives, false))
+                   options::OPT_fno_use_line_directives, IsWindowsMSVC))
     CmdArgs.push_back("-fuse-line-directives");
 
   // -fms-compatibility=0 is default.