[PATCH] Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c

[Jonathan Nieder]

H.J. Lu wrote:

> Replace = with += in CFLAGS-xxx.c and CPPFLAGS-xxx.c to allow Makefile
> under sysdeps to define CFLAGS-xx.c and CPPFLAGS-xxx.c.
>
> OK for master?

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Thanks.