Don't use empty space after variable in Android makefile

In Android makefile, we always assign a value to a variable. But if we add one or more empty space after variable value, it may cause some build error.

For example, If we want to add a preinstall apk to system, we may use makefile template such as below:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE := LeanbackSampleApp
LOCAL_SRC_FILES := $(LOCAL_MODULE).apk
LOCAL_MODULE_CLASS := APPS
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE_SUFFIX := $(COMMON_ANDROID_PACKAGE_SUFFIX)
LOCAL_CERTIFICATE := platform

include $(BUILD_PREBUILT)

Above makefile template is copied from AOSP. The template is simply, but if we add empty space after LeanbackSampleApp, the build system will use 'LeanbackSampleApp .apk' to find local src files, which will cause build error.

The build system does not trim the variable value, which careless operation will cause absurd error. Unfortunatelly, a company’s development intern has encountered this problem today.