fix releasetools for non-linux architectures

The ota and img building scripts contained some hardcoded 'linux-x86'
paths.  Remove and replace with a slightly redefined -p option.
Modify Makefile to pass correct -p when building.
diff --git a/core/Makefile b/core/Makefile
index b1420b5..5e5c735 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -880,6 +880,7 @@
 $(INTERNAL_OTA_PACKAGE_TARGET): $(BUILT_TARGET_FILES_PACKAGE) otatools
 	@echo "Package OTA: $@"
 	$(hide) ./build/tools/releasetools/ota_from_target_files \
+	   -p $(HOST_OUT) \
            -b $(TARGET_DEVICE_DIR)/BoardConfig.mk \
            -k $(KEY_CERT_PAIR) \
            $(BUILT_TARGET_FILES_PACKAGE) $@
@@ -1005,6 +1006,7 @@
 $(INTERNAL_UPDATE_PACKAGE_TARGET): $(BUILT_TARGET_FILES_PACKAGE) otatools
 	@echo "Package: $@"
 	$(hide) ./build/tools/releasetools/img_from_target_files \
+	   -p $(HOST_OUT) \
 	   -b $(TARGET_DEVICE_DIR)/BoardConfig.mk \
 	   $(BUILT_TARGET_FILES_PACKAGE) $@