Add android_ninja, like android_make for ninja.

platform_tools/android/bin/android_make

 #!/bin/bash
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
 # remove the existing .android_config file prior to running android_setup. If
 # we did not remove this here then we would build for whatever device type was
 # listed in the .android_config instead of the default device type.
 if [ -f .android_config ]
 then
   rm .android_config
@@ skipping 21 matching lines @@
 done
 
 if [[ -n "$ANDROID_MAKE_CCACHE" ]]; then
   $ANDROID_MAKE_CCACHE --version &> /dev/null
   if [[ "$?" != "0" ]]; then
     echo "Unable to find ccache!"
     exit 1
   fi
 fi
 
+# Use the "android" flavor of the Makefile generator for both Linux and OS X.
+exportVar GYP_GENERATORS "make-android"
 make ${makeVars[@]}
 if [ $? != 0 ]
 then
   exit 1;
 fi