#36 configure.ac: add --without-execinfo option

[Fabrice Fontaine]

Add an option to allow the user to disable execinfo to avoid the following build failure on musl with https://github.com/mikroskeem/libexecinfo:

/home/buildroot/autobuild/instance-3/output-1/host/opt/ext-toolchain/bin/../lib/gcc/x86_64-buildroot-linux-musl/10.3.0/../../../../x86_64-buildroot-linux-musl/bin/ld: /home/buildroot/autobuild/instance-3/output-1/build/openipmi-2.0.28/utils/.libs/libOpenIPMIutils.so: undefined reference to `backtrace'

Fixes:

• http://autobuild.buildroot.org/results/dcc33c5cca97d538231647a94212450f043974b3

[Corey Minyard]

This is not really the right way to fix this. You need to check for the backtrace() function, really. This can be done automatically. Adding flags should always be a last resort for things like this.