remember device-specific releasetools extensions in target-files

Store the location of the releasetools extensions in the target-files
zip, and make ota_from_target_files use that stored location by
default (though it can still be overridden with -s if desired).

core/Makefile

@@ -814,6 +814,13 @@ $(BUILT_TARGET_FILES_PACKAGE): PRIVATE_OTA_TOOLS := $(built_ota_tools)
 
 $(BUILT_TARGET_FILES_PACKAGE): PRIVATE_RECOVERY_API_VERSION := $(RECOVERY_API_VERSION)
 
+ifeq ($(TARGET_RELEASETOOLS_EXTENSIONS),)
+# default to common dir for device vendor
+$(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_DEVICE_DIR)/../common
+else
+$(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_RELEASETOOLS_EXTENSIONS)
+endif
+
 # Depending on the various images guarantees that the underlying
 # directories are up-to-date.
 $(BUILT_TARGET_FILES_PACKAGE): \
@@ -887,6 +894,7 @@ endif
 	$(hide) echo "recovery $(call image-size-from-data-size,$(BOARD_RECOVERYIMAGE_PARTITION_SIZE))" >> $(zip_root)/META/imagesizes.txt
 	$(hide) echo "system $(call image-size-from-data-size,$(BOARD_SYSTEMIMAGE_PARTITION_SIZE))" >> $(zip_root)/META/imagesizes.txt
 	$(hide) echo "userdata $(call image-size-from-data-size,$(BOARD_USERDATAIMAGE_PARTITION_SIZE))" >> $(zip_root)/META/imagesizes.txt
+	$(hide) echo "$(tool_extensions)" > $(zip_root)/META/tool-extensions.txt
 	@# Zip everything up, preserving symlinks
 	$(hide) (cd $(zip_root) && zip -qry ../$(notdir $@) .)
 
@@ -909,13 +917,6 @@ INTERNAL_OTA_PACKAGE_TARGET := $(PRODUCT_OUT)/$(name).zip
 
 $(INTERNAL_OTA_PACKAGE_TARGET): KEY_CERT_PAIR := $(DEFAULT_KEY_CERT_PAIR)
 
-ifeq ($(TARGET_RELEASETOOLS_EXTENSIONS),)
-# default to common dir for device vendor
-$(INTERNAL_OTA_PACKAGE_TARGET): extensions := $(TARGET_DEVICE_DIR)/../common
-else
-$(INTERNAL_OTA_PACKAGE_TARGET): extensions := $(TARGET_RELEASETOOLS_EXTENSIONS)
-endif
-
 ifeq ($(TARGET_OTA_SCRIPT_MODE),)
 # default to "auto"
 $(INTERNAL_OTA_PACKAGE_TARGET): scriptmode := auto
@@ -926,7 +927,7 @@ endif
 $(INTERNAL_OTA_PACKAGE_TARGET): $(BUILT_TARGET_FILES_PACKAGE) otatools
 	@echo "Package OTA: $@"
 	$(hide) ./build/tools/releasetools/ota_from_target_files \
-	   -s $(extensions) -m $(scriptmode) \
+	   -m $(scriptmode) \
 	   -p $(HOST_OUT) \
            -k $(KEY_CERT_PAIR) \
            $(BUILT_TARGET_FILES_PACKAGE) $@

tools/releasetools/common.py

@@ -440,7 +440,7 @@ class DeviceSpecificParams(object):
 
     if self.module is None:
       path = OPTIONS.device_specific
-      if path is None: return
+      if not path: return
       try:
         if os.path.isdir(path):
           info = imp.find_module("releasetools", [path])

tools/releasetools/ota_from_target_files

@@ -57,6 +57,7 @@ if sys.hexversion < 0x02040000:
   sys.exit(1)
 
 import copy
+import errno
 import os
 import re
 import sha
@@ -855,6 +856,23 @@ def main(argv):
   print "unzipping target target-files..."
   OPTIONS.input_tmp = common.UnzipTemp(args[0])
 
+  if OPTIONS.device_specific is None:
+    # look for the device-specific tools extension location in the input
+    try:
+      f = open(os.path.join(OPTIONS.input_tmp, "META", "tool-extensions.txt"))
+      ds = f.read().strip()
+      f.close()
+      if ds:
+        ds = os.path.normpath(ds)
+        print "using device-specific extensions in", ds
+        OPTIONS.device_specific = ds
+    except IOError, e:
+      if e.errno == errno.ENOENT:
+        # nothing specified in the file
+        pass
+      else:
+        raise
+
   common.LoadMaxSizes()
   if not OPTIONS.max_image_size:
     print