cross-compiling difficulties caused by running compiled programs during build

[George McCollister]

Anyone who has cross-compiled very many packages using autotools can
tell you that one major source of problems is when packages use $(CC)
to build a utility which is then executed to generate a file (often a
header) which is required for the build to proceed. Running an arm
binary on an x86_64 doesn't usually work unless you've tricked your
operating system into executing such files with an emulator :) From
what I've seen there seems to be several non-standard approaches to
dealing with this issue.

The first and most obvious solution is to do nothing and just try to
execute the host binary on the build machine.
Example:
https://fedorahosted.org/audit/browser/trunk/lib/Makefile.am lines 61-64

Another approach I've found is to use ac_prog_cc_for_build or
ax_prog_cc_for_build as described here:
http://www.gnu.org/software/autoconf-archive/ax_prog_cc_for_build.html
an example of this can be found in libgpg-error:
http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgpg-error.git;a=blob;f=m4/ac_prog_cc_for_build.m4;h=42c91ce355271d614fde1ddb876302e28918272e;hb=HEAD
http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgpg-error.git;a=blob;f=configure.ac;h=ee42f9e43a63606d10cf86f09a41d0ff8ec0fe61;hb=HEAD
(lines: 74-85)
http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgpg-error.git;a=blob;f=src/Makefile.am;h=a84e3f0a65a99c7b6df6631cdca6b3043b3db6f7;hb=HEAD
(lines: 168-177)

The final approach seems to be accepting a configure switch or
environment variable to override the path of the program used so a
native version can be supplied instead.

Is there a correct approach to dealing with this issue? Is there
anything the authors of autotools could and should do to address this
going forward?

Cheers,
George McCollister