Merge pull request #1796 from Homebrew/revert-1746-always-filter-flags-deps

Revert "cc: always filter flags on deps."

Library/Homebrew/shims/super/cc

@@ -206,6 +206,10 @@ class Cmd
   end
 
   def keep?(path)
+    # The logic in this method will eventually become the default,
+    # but is currently opt-in.
+    return keep_orig?(path) unless ENV["HOMEBREW_EXPERIMENTAL_FILTER_FLAGS_ON_DEPS"]
+
     # Allow references to self
     if formula_prefix && path.start_with?("#{formula_prefix}/")
       true
@@ -222,6 +226,11 @@ class Cmd
     end
   end
 
+  # The original less-smart version of keep_orig; will eventually be removed
+  def keep_orig?(path)
+    path.start_with?(prefix, cellar, tmpdir) || !path.start_with?("/opt/local", "/opt/boxen/homebrew", "/opt/X11", "/sw", "/usr/X11")
+  end
+
   def cflags
     args = []