i dont quite understand/agree with the last few comments, but i guess it doesnt
matter that much since the code now uses AC_PATH_TOOL which is all i wanted ;)

i'm not requesting you install HOST prefixed wrappers. that would actually be
worse since people setting up cross-compile environments already generically
take care of this issue.

AC_PATH_TOOL will fall back to gpg-error-config, so the default behavior is
unchanged. AC_PATH_PROG however will wrongly select the host's gpg-error-config
which breaks cross-compiling. it isnt up to random packages to manage the HOST
prefixed tools, so the gpg-error package not explicitly installing it is
irrelevant. cross-build systems take care of creating the wrappers automatically.