gptfdisk: ensure correct libintl/libiconv build order

Fixes:
http://autobuild.buildroot.net/results/c7d/c7d48554d76e39cbdf715721ae51e3516a99f97e/



We're explicitly linking against libintl/libiconv if enabled when linking
statically, but weren't ensuring that those libraries had already been built
before gptfdisk leading to linker issues.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>