png.o: In function `load_image':
png.c:(.text+0xa5a): undefined reference to `png_read_destroy'
png.o: In function `save_image':
png.c:(.text+0x19d7): undefined reference to `png_write_destroy'
collect2: ld returned 1 exit status
make[3]: *** [png] Error 1
make[3]: *** Waiting for unfinished jobs....
make[3]: Leaving directory `/var/tmp/portage/gimp-2.2.8-r1/work/gimp-2.2.8/plug-ins/common'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/var/tmp/portage/gimp-2.2.8-r1/work/gimp-2.2.8/plug-ins'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/var/tmp/portage/gimp-2.2.8-r1/work/gimp-2.2.8'
make: *** [all] Error 2

!!! ERROR: media-gfx/gimp-2.2.8-r1 failed.
Call stack:
  ebuild.sh, line 1539:   Called dyn_compile
  ebuild.sh, line 939:   Called src_compile
  gimp-2.2.8-r1.ebuild, line 138:   Called die

!!! (no error message)
!!! If you need support, post the topmost build error, and the call stack if relevant.