3.4.2 fails to compile on non-x86 architectures

Just a note that 3.4.1 was OK, but 3.4.2 fails to build on all of
Fedora's non x86 architectures: ppc64, ppc64le, aarch64 and armv7hl:

https://koji.fedoraproject.org/koji/taskinfo?taskID=17528373

A sample build log (from ppc64) is at
https://kojipkgs.fedoraproject.org//work/tasks/8377/17528377/build.log

The failure is down in the link phase, with multiple instances of:

./.libs/libamanda.so: undefined reference to `get_sse42'

This commit appears to be the cuplrit:

https://github.com/zmanda/amanda/commit/8e08855b9edb841ff30b5f7e137529cfc95899d3#diff-552be1e0690d6f1201be6fa10621fa77L2119

A member of the Fedora alternative arch team offered to have a go; he
suggested that providing an empty have_sse42() function on non-x86 would
do the trick, and even though I rather suck at C I may have a try at
fixing this if I can find a few minutes.

 - J<