Fix skcms Mac build job

Change-Id: I67fdcafba11e826b2ac0d42e081298f4dd302ec3
Reviewed-on: https://skia-review.googlesource.com/145733
Auto-Submit: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/infra/bots/bot.py b/infra/bots/bot.py
index a6c937d..e48cec8 100644
--- a/infra/bots/bot.py
+++ b/infra/bots/bot.py
@@ -17,6 +17,9 @@
                                                cwd=os.getcwd())
 
 if 'darwin' in sys.platform:
+  # TODO(dogben): Figure out how to get Xcode from CIPD.
+  call('sudo xcode-select -switch /Applications/Xcode9.2.app')
+
   # Our Mac bots don't have a real GCC installed.
   append('skcms/build/gcc', 'disabled = true')