AIX: Enable usage of fetch and gclient

Change-Id: I4fe559cb44ccd9c6b037b7b096b088adf652ef9b
Reviewed-on: https://chromium-review.googlesource.com/1102718
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>

cipd

@@ -28,7 +28,7 @@ case $UNAME in
     PLAT=mac
     ;;
   *)
-    echo "UNKNOWN OS: $UNAME"
+    echo "cipd not supported on $UNAME"
     exit 1
 esac
 

download_from_google_storage.py

@@ -34,6 +34,8 @@ PLATFORM_MAPPING = {
     'darwin': 'mac',
     'linux2': 'linux',
     'win32': 'win',
+    'aix6': 'aix',
+    'aix7': 'aix',
 }