gn: don't reject absolute unix style pathnames in labels

tools/gn/label.cc

Index: tools/gn/label.cc
diff --git a/tools/gn/label.cc b/tools/gn/label.cc
index 65fcef82d759bb00a57a9d95ef4ebde53ea04e7a..11dbae5750fe398e790f97b082cbfcd82528f9a9 100644
--- a/tools/gn/label.cc
+++ b/tools/gn/label.cc
@@ -35,15 +35,6 @@ bool ComputeBuildLocationFromDep(const Value& input_value,
     return true;
   }
 
-  // Don't allow directories to start with a single slash. All labels must be
-  // in the source root.
-  if (input[0] == '/' && (input.size() == 1 || input[1] != '/')) {

[tfarina, 2014/12/30 02:38:00]

OK. let's try.

-    *err = Err(input_value, "Label can't start with a single slash",
-        "Labels must be either relative (no slash at the beginning) or be "
-        "absolute\ninside the source root (two slashes at the beginning).");
-    return false;
-  }
-
   *result = current_dir.ResolveRelativeDir(input);
   return true;
 }