meson.eclass: Set needs_exe_wrapper in cross file

meson.eclass: Set needs_exe_wrapper in cross file

needs_exe_wrapper tells meson whether the build machine is able to
directly execute the binaries it produces or whether it needs an exe
wrapper (like QEMU). For non-native ABI builds like building 32-bit
libraries on an x86-64 system, we want this set to false to communicate
to meson that the build machine can run the binaries directly.

Reviewed-by: Mike Gilbert <floppym@gentoo.org>
Signed-off-by: Matt Turner <mattst88@gentoo.org>