Apply the version fixup in order to solve the following build error on systems
not using exactly gettext version 0.18:

    make[6]: Entering directory '.../build_dir/target-mips_34kc_musl-1.1.14/mc-4.8.17/po'
    *** error: gettext infrastructure mismatch: using a Makefile.in.in from gettext version 0.18 but the autoconf macros are from gettext version 0.19

The fixup will ensure that embedded macro versions are replaced with the
version of the staged gettext executable in ./staging_dir/host/bin

Signed-off-by: Jo-Philipp Wich <jo@mein.io>