Log Message:
qemu: avoid meson's heuristic use of GCC "response files" [1]

This should fix gettext linkage errors when building qemu with the
gtk3 option enabled.

[1] Response files pass compiler arguments to GCC in a text file when
meson thinks the command line is too long. pkgsrc wrappers are not able
to inspect and transform those which leads to difficult-to-debug problems.
meson has a default command line threshold of 64k. Bump this to 256k
which is the default value of kern.argmax on NetBSD.