msvc helper: drop system includes

Drop any #includes that look like they're referencing system headers.
This reduces the dependency information considerably.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/msvc_helper.h b/src/msvc_helper.h
index 5bf9787..41b9f9b 100644
--- a/src/msvc_helper.h
+++ b/src/msvc_helper.h
@@ -16,8 +16,6 @@
 #include <vector>
 using namespace std;
 
-struct StringPiece;
-
 /// Visual Studio's cl.exe requires some massaging to work with Ninja;
 /// for example, it emits include information on stderr in a funny
 /// format when building with /showIncludes.  This class wraps a CL
@@ -34,6 +32,11 @@ struct CLWrapper {
   /// Exposed for testing.
   static string FilterShowIncludes(const string& line);
 
+  /// Return true if a mentioned include file is a system path.
+  /// Expects the path to already by normalized (including lower case).
+  /// Filtering these out reduces dependency information considerably.
+  static bool IsSystemInclude(const string& path);
+
   /// Parse a line of cl.exe output and return true if it looks like
   /// it's printing an input filename.  This is a heuristic but it appears
   /// to be the best we can do.