Make skydb --gdb work a bit better on Android

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/878163005
diff --git a/sky/tools/android_library_cacher.py b/sky/tools/android_library_cacher.py
index db80d18..564448a 100755
--- a/sky/tools/android_library_cacher.py
+++ b/sky/tools/android_library_cacher.py
@@ -4,11 +4,12 @@
 # found in the LICENSE file.
 
 import argparse
-import re
-import sys
-import os
 import logging
+import os
+import re
+import skypy.paths
 import subprocess
+import sys
 
 SRC_ROOT = skypy.paths.Paths('ignored').src_root
 ADB_PATH = os.path.join(SRC_ROOT,
diff --git a/sky/tools/skydb b/sky/tools/skydb
index 66023c9..67e951a 100755
--- a/sky/tools/skydb
+++ b/sky/tools/skydb
@@ -126,7 +126,7 @@
                 '--args-for=mojo:native_viewport_service --use-osmesa')
 
         if is_android and args.gdb:
-            shell_args.append('--wait_for_debugger')
+            shell_args.append('--wait-for-debugger')
 
         if 'remote_sky_server_port' in self.pids:
             shell_command = self._wrap_for_android(shell_args)
@@ -180,6 +180,11 @@
         gn_args = gn_args_from_build_dir(self.paths.build_dir)
         is_android = 'android_sdk_version' in gn_args
 
+        if is_android and args.gdb and not 'is_debug' in gn_args:
+            # FIXME: We don't include gdbserver in the release APK...
+            print "Cannot debug Release builds on Android"
+            sys.exit(2)
+
         sky_server = self.sky_server_for_args(args)
         self.pids['sky_server_pid'] = sky_server.start()
         self.pids['sky_server_port'] = sky_server.port
@@ -265,7 +270,7 @@
             # We could just run gdb_attach_command here, but when I do that
             # it auto-suspends in my zsh.  Unclear why.
             # self.gdb_attach_command(args)
-            print "Run skydb gdb_attach to attach."
+            print "Run 'skydb gdb_attach' to attach."
 
     def _kill_if_exists(self, key, name):
         pid = self.pids.pop(key, None)