Selective build clobbering feature (landmines.py and android build scripts).

build/android/buildbot/buildbot_functions.sh

Index: build/android/buildbot/buildbot_functions.sh
diff --git a/build/android/buildbot/buildbot_functions.sh b/build/android/buildbot/buildbot_functions.sh
index 25e89c40a82f98eaf69a4cf47b791dd935c712bd..f55729c809a1976a27b6225ef4b341621b3ccd4e 100755
--- a/build/android/buildbot/buildbot_functions.sh
+++ b/build/android/buildbot/buildbot_functions.sh
@@ -47,20 +47,31 @@ function bb_baseline_setup {
   shift
   cd $SRC_ROOT
 
-  if [[ $BUILDBOT_CLOBBER ]]; then
+  echo "@@@BUILD_STEP Parse args@@@"
+  bb_parse_args "$@"
+
+  local out_path="${SRC_ROOT}/out/${BUILDTYPE}"
+  local trigger_path="$out_path/.landmines_triggered"
+
+  if [[ $BUILDBOT_CLOBBER || -f "$trigger_path" ]]; then
     echo "@@@BUILD_STEP Clobber@@@"
+
+    if [[ -f "$trigger_path" ]]; then
+      echo "Clobbering due to triggered landmines: "
+      cat "$trigger_path"
+    fi
+
     # Sdk key expires, delete android folder.
     # crbug.com/145860
     rm -rf ~/.android
-    rm -rf "${SRC_ROOT}"/out
-    if [ -e "${SRC_ROOT}"/out ] ; then
-      echo "Clobber appeared to fail?  ${SRC_ROOT}/out still exists."
+    rm -rf "$out_path"
+    if [ -e "$out_path" ] ; then
+      echo "Clobber appeared to fail?  $out_path still exists."
       echo "@@@STEP_WARNINGS@@@"
     fi
   fi
 
   echo "@@@BUILD_STEP Environment setup@@@"
-  bb_parse_args "$@"
 
   local BUILDTOOL=$(bb_get_json_prop "$FACTORY_PROPERTIES" buildtool)
   if [[ $BUILDTOOL = ninja ]]; then