http://stackoverflow.com/questions/6595208/what-does-this-line-mean-local-export-c-includes
LOCAL_EXPORT_C_INCLUDES和LOCALC_INCLUDES 的差別。同理LOCAL_EXPORT_CFLAGS與LOCAL_CFLAGS也一樣
編譯某模塊是，如果它依賴別的模塊，那么別的模塊的LOCAL_EXPORT*類的值，會自動加入到本模塊。（但是反過來不會有作用）
LOCAL_EXPORT_CFLAGS
Define this variable to record a set of C/C++ compiler flags that will
be added to the LOCAL_CFLAGS definition of any other module that uses
this one with LOCAL_STATIC_LIBRARIES or LOCAL_SHARED_LIBRARIES.
For example, consider the module 'foo' with the following definition:
include $(CLEAR_VARS) LOCAL_MODULE := foo LOCAL_SRC_FILES := foo/foo.c LOCAL_EXPORT_CFLAGS :=-DFOO=1 include $(BUILD_STATIC_LIBRARY)And another module, named 'bar' that depends on it as:
include $(CLEAR_VARS) LOCAL_MODULE := bar LOCAL_SRC_FILES := bar.c LOCAL_CFLAGS :=-DBAR=2 LOCAL_STATIC_LIBRARIES := foo include $(BUILD_SHARED_LIBRARY) Then, the flags '-DFOO=1 -DBAR=2' will be passed to the compiler when
building bar.c
Exported flags are prepended to your module's LOCAL_CFLAGS so you can
easily override them. They are also transitive: if 'zoo' depends on
'bar' which depends on 'foo', then 'zoo' will also inherit all flags
exported by 'foo'.
Finally, exported flags are not used when building the module that
exports them. In the above example, -DFOO=1 would not be passed to the
compiler when building foo/foo.c.
LOCAL_EXPORT_CPPFLAGS
Same as LOCAL_EXPORT_CFLAGS, but for C++ flags only.
LOCAL_EXPORT_C_INCLUDES
Same as LOCAL_EXPORT_CFLAGS, but for C include paths.
This can be useful if 'bar.c' wants to include headers
that are provided by module 'foo'.