Cross-compilation fails in 2.58
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=908334
Since version 2.58.0-1, glib2.0 fails to cross build from source, because it fails to find testmarshal.h in tests/gobject. The rules for generating it are conditional to !CROSS_COMPILING, because they run glib-genmarshall.
Presumably this was masked by Autotools tarballs containing a pre-generated testmarshal.h, but 2.58.x tarballs were built with Meson so they don't contain pre-generated detritus.