package/axfsutils: fix Makefile

mkfs.axfs uses zlib, but does not have an rpath to our host dir.

That's because:
  - we're not passing our host CFLAGS or LDFLAGS
  - it is forcibly setting CFLAGS in the Makefile, overriding anything
    specified by the user
  - it is not using LDFLAGS at all

Add two patches so that CFLAGS and LDFLAGS from the environment are
used if present.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Tested-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>