see upstream bug at https://bugzilla.xamarin.com/show_bug.cgi?id=39112

Description of problem:
Mono 4.3.1 Cycle 7 Alpha fails to build in s390x.

see the build log of a scratch build at http://s390.koji.fedoraproject.org/kojifiles/work/tasks/6391/2106391/build.log

aot-compiler.c: In function 'mono_aot_get_direct_call_symbol':
aot-compiler.c:7739:11: error: implicit declaration of function 'get_pinvoke_import' [-Werror=implicit-function-declaration]
     sym = get_pinvoke_import (llvm_acfg, method);
           ^~~~~~~~~~~~~~~~~~

I checked the code at https://github.com/mono/mono/blob/ba2e5e42f342f2b64fedc3cee2ef925c57c4a325/mono/mini/aot-compiler.c#L7739
and noticed that the function get_pinvoke_import is defined in line 4734 inside an ifdef MONO_ARCH_AOT_SUPPORTED, but in line 7739 that ifdef is missing.