Supply "-extldflags -fno-PIC" to locksmith GOLDFLAGS on hardened gcc

A similar workaround is utilized in the docker ebuild, see:
https://bugs.gentoo.org/show_bug.cgi?id=493328
Merge pull request #917 from vcaputo/locksmith_hardened_gcc_workaround

Supply "-extldflags -fno-PIC" to locksmith GOLDFLAGS on hardened gcc