Fix target arch for x86 bots.

The target_arch should be ia32 for x86 builders. This is causing the x86 try and
fyi bots to fail during runhooks because it doesnt match a case in common.gypi.

BUG=359644
TBR=cmp@chromium.org

Review URL: https://codereview.chromium.org/581173004

Cr-Commit-Position: refs/heads/master@{#295644}

build/android/buildbot/bb_run_bot.py

@@ -158,12 +158,12 @@ def GetBotStepMap():
         T(['chromedriver'], ['--install=ChromeShell', '--skip-wipe',
           '--cleanup'])),
       B('fyi-x86-builder-dbg',
-        H(compile_step + std_host_tests, experimental, target_arch='x86')),
+        H(compile_step + std_host_tests, experimental, target_arch='ia32')),
       B('fyi-builder-dbg',
         H(std_build_steps + std_host_tests, experimental,
           extra_gyp='emma_coverage=1')),
       B('x86-builder-dbg',
-        H(compile_step + std_host_tests, target_arch='x86')),
+        H(compile_step + std_host_tests, target_arch='ia32')),
       B('fyi-builder-rel', H(std_build_steps,  experimental)),
       B('fyi-tests', H(std_test_steps),
         T(std_tests + chrome_sync_shell_tests,