The apr-config script can automatically adjust its paths to help with
cross-compiling, but it only does this if apr itself was originally
cross-compiled, which may not be the case. Forcing it to consider that
it might be cross-compiled doesn't do any harm though.

Bug: https://bugs.gentoo.org/931829

diff -Naur a/apr-config.in b/apr-config.in
--- a/apr-config.in	2023-03-13 10:29:04.000000000 +0000
+++ b/apr-config.in	2024-05-14 10:23:28.429984195 +0100
@@ -48,7 +48,7 @@
 # NOTE: the following line is modified during 'make install': alter with care!
 location=@APR_CONFIG_LOCATION@
 
-cross_compiling=@APR_CROSS_COMPILING@
+cross_compiling=maybe
 
 if test "$cross_compiling" != "no"; then