Bug#1116552: meson: env2mfile should use ${DEB_HOST_GNU_TYPE}-vapigen if available

[Simon McVittie]

Control: tags -1 + fixed-upstream

On Sun, 28 Sep 2025 at 15:17:59 +0100, Simon McVittie wrote:
>valac (>= 0.56.18-3) provides a script per host architecture named
>${DEB_HOST_GNU_TYPE}-vapigen. If this executable exists, Meson should
>use it during cross-builds, falling back to the unprefixed vapigen
>otherwise.

Change merged in upstream git, will presumably be in 1.10.0 (possibly 
1.9.2, I don't know the specifics of the upstream stable-branch 
policies).

     smcv