Support Visual C++ PGO in Ninja generator

pylib/gyp/msvs_emulation.py

Index: pylib/gyp/msvs_emulation.py
===================================================================
--- pylib/gyp/msvs_emulation.py	(revision 1797)
+++ pylib/gyp/msvs_emulation.py	(working copy)
@@ -487,7 +487,10 @@
         map={'1': ':NO', '2': ''}, prefix='/NXCOMPAT')
     ld('OptimizeReferences', map={'1': 'NOREF', '2': 'REF'}, prefix='/OPT:')
     ld('EnableCOMDATFolding', map={'1': 'NOICF', '2': 'ICF'}, prefix='/OPT:')
-    ld('LinkTimeCodeGeneration', map={'1': '/LTCG'})
+    ld('LinkTimeCodeGeneration',

[scottmg, 2013/11/23 17:15:13]

(Sorry, not at a Windows machine right now to check...) Does the Librarian
section also need to be modified to either 1) handle '1' instead of 'true', or
2) also handle the other LTCG options?

[yukawa, 2013/11/25 14:04:12]

Yeah, I believe that the Librarian should continue to use boolean since the
underlying MSVS object model uses bool as follows.
| bool LinkTimeCodeGeneration { get; set; } 
http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.vcprojectengin...

Actually Skia is specifying both settings correctly.
https://code.google.com/p/skia/source/browse/trunk/gyp/common_conditions.gypi...

Does this make sense?

+        map={'1': '', '2': ':PGINSTRUMENT', '3': ':PGOPTIMIZE',
+             '4': ':PGUPDATE'},
+        prefix='/LTCG')
     ld('IgnoreDefaultLibraryNames', prefix='/NODEFAULTLIB:')
     ld('ResourceOnlyDLL', map={'true': '/NOENTRY'})
     ld('EntryPointSymbol', prefix='/ENTRY:')