Merge pull request #37 from pedrokiefer/patch-1

zlib must use -isystem

Author: pcj

protobuf/build_file/com_github_madler_zlib.BUILD

@@ -38,6 +38,9 @@ cc_library(
         "zlib.h",
         "zutil.h",
     ],
+    includes = [
+        ".",
+    ],
     copts = [
         "-Wno-unused-variable",
         "-Wno-implicit-function-declaration",