glib-2.0: add -march=i486 into CFLAGS automatically when needed.

glib-2.0: add -march=i486 into CFLAGS automatically when needed.

glib configure will check if current gcc need -march=i486,
when gcc need -march=i486 but CFLAGS don't have,
glib configure will abort and advise the user to add -march=i486.
This will break the build process,it's not good for automatic build system.
so change this to adding -march=i486 automatically when it is needed.

Signed-off-by: Song.Li <Song.Li@windriver.com>
Signed-off-by: Jackie Huang <jackie.huang@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>