As per Meson 0.56.0:
 https://mesonbuild.com/Machine-files.html#properties

Not necessary anymore since Meson 0.50.0:
 https://mesonbuild.com/Release-notes-for-0-50-0.html#libdir-defaults-to-lib-when-cross-compiling

Prepare to add some code around the _build() call.

Allows running the unit tests on Linux.

Commit
https://github.com/mesonbuild/meson/commit/08224dafcba1b694fb624553e7d84deb565aae22
changed Meson to require BOOST_ROOT for cross builds.

So long, autotools!  This is my last MPD related project to migrate
away from it.  It has its strengths, but also very obvious weaknesses
and weirdnesses.  Today, many of its quirks are not needed anymore,
and are cumbersome and slow.  Now welcome our new Meson overlords!

Prevent Meson from running Android-x86 binaries.  That will fail
because the Android standard libraries are most likely not installed.