gn, mac: Add sysroot.gni for Mac that finds default SDK

Bug: crashpad:79
Change-Id: Ida1b80f17374b283267cc60bed295a7bebb50755
Reviewed-on: https://chromium-review.googlesource.com/812410
Reviewed-by: Mark Mentovai <mark@chromium.org>

build/find_mac_sdk.py

diff --git a/build/find_mac_sdk.py b/build/find_mac_sdk.py
new file mode 100755
index 0000000..9c9165a
--- /dev/null
+++ b/build/find_mac_sdk.py
@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+
+# Copyright 2017 The Crashpad Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import subprocess
+import sys
+
+
+def main(args):
+  if len(args) != 0:
+    print('usage: find_mac_sdk.py', file=sys.stderr)
+    return 1
+
+  subprocess.check_call(['xcrun', '--show-sdk-path'])
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))

build/sysroot.gni

diff --git a/build/sysroot.gni b/build/sysroot.gni
new file mode 100644
index 0000000..d527812
--- /dev/null
+++ b/build/sysroot.gni
@@ -0,0 +1,19 @@
+# Copyright 2017 The Crashpad Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# TODO(scottmg): Use this file on Fuchsia too.
+
+if (is_mac) {
+  sysroot = exec_script("find_mac_sdk.py", [], "trim string")
+}