Pass the mspdbsrv flag as a command line argument to the link wrapper.

pylib/gyp/generator/ninja.py

Index: pylib/gyp/generator/ninja.py
===================================================================
--- pylib/gyp/generator/ninja.py	(revision 1834)
+++ pylib/gyp/generator/ninja.py	(working copy)
@@ -1606,10 +1606,12 @@
                'resname': resource_name,
                'embed': embed_manifest }
   rule_name_suffix = _GetWinLinkRuleNameSuffix(embed_manifest)
+  use_separate_mspdbsrv = (
+      int(os.environ.get('GYP_USE_SEPARATE_MSPDBSRV', '0')) != 0)
   dlldesc = 'LINK%s(DLL) $binary' % rule_name_suffix.upper()
-  dllcmd = ('%s gyp-win-tool link-wrapper $arch '
+  dllcmd = ('%s gyp-win-tool link-wrapper $arch %s '
             '$ld /nologo $implibflag /DLL /OUT:$binary '
-            '@$binary.rsp' % sys.executable)
+            '@$binary.rsp' % (sys.executable, use_separate_mspdbsrv))
   dllcmd = FullLinkCommand(dllcmd, '$binary', 'dll')
   master_ninja.rule('solink' + rule_name_suffix,
                     description=dlldesc, command=dllcmd,
@@ -1625,9 +1627,9 @@
                     pool='link_pool')
   # Note that ldflags goes at the end so that it has the option of
   # overriding default settings earlier in the command line.
-  exe_cmd = ('%s gyp-win-tool link-wrapper $arch '
+  exe_cmd = ('%s gyp-win-tool link-wrapper $arch %s '
              '$ld /nologo /OUT:$binary @$binary.rsp' %
-              sys.executable)
+              (sys.executable, use_separate_mspdbsrv))
   exe_cmd = FullLinkCommand(exe_cmd, '$binary', 'exe')
   master_ninja.rule('link' + rule_name_suffix,
                     description='LINK%s $binary' % rule_name_suffix.upper(),