ART: Add ART_TEST_DONT_REBOOT_DEVICE flag.

Adds a flag to prevent the device from rebooting
during buildbot-setup-device.sh. This is useful when
running on Arm FVP - 'adb reboot' doesn't restart it
properly.

Test: test-art-target.
Change-Id: I9ff85c974da8248d35af0c9360fd38ace3c27f7e
diff --git a/tools/buildbot-setup-device.sh b/tools/buildbot-setup-device.sh
index b139c47..10f526c 100755
--- a/tools/buildbot-setup-device.sh
+++ b/tools/buildbot-setup-device.sh
@@ -101,7 +101,7 @@
 echo -e "${green}Kill stalled dalvikvm processes${nc}"
 # 'ps' on M can sometimes hang.
 timeout 2s adb shell "ps" >/dev/null
-if [ $? = 124 ]; then
+if [[ $? == 124 ]] && [[ "$ART_TEST_DONT_REBOOT_DEVICE" != true ]]; then
   echo -e "${green}Rebooting device to fix 'ps'${nc}"
   adb reboot
   adb wait-for-device root