openslp does not build universal

[ryandesign@…]

(cd .libs/libslp.lax/libcommonlibslp.a && ar x /opt/local/var/macports/build/_Users_rschmidt_macports_dports_devel_openslp/work/openslp-1.2.1/libslp/../common/.libs/libcommonlibslp.a)
ar: /opt/local/var/macports/build/_Users_rschmidt_macports_dports_devel_openslp/work/openslp-1.2.1/libslp/../common/.libs/libcommonlibslp.a is a fat file (use libtool(1) or lipo(1) and ar(1) on it)
ar: /opt/local/var/macports/build/_Users_rschmidt_macports_dports_devel_openslp/work/openslp-1.2.1/libslp/../common/.libs/libcommonlibslp.a: Inappropriate file type or format
make[2]: *** [libslp.la] Error 1

[rmstonecipher@…]

Added 'universal_variant no' in r73792 to ensure openslp builds for 64-bit Intel even if +universal is selected by default.

[rmstonecipher@…]

I felt like trying a little harder instead of weaseling out with 'universal_variant no'.
A post-configure routine which resolved non-universality of smpeg and exif also fixes +universal building for openslp in r73793.

[jmr@…]

Linking an installed file into the build directory has always seemed like a bad idea to me. What if the build system decides to write to it?