arpack default variant not handled correctly

[anddam (Andrea D'Amore)]

The default_variant if condition in Portfile is placed after the if/elseif/else that executes 'set gccversion 4.x'.

This way when no variant is explicitly selected gccversion is set to 4.5, the last else branch, even if default_variant is gcc44.

The build breaks and there are gcc45 references in compiler linker flags:

shell command "cd /opt/local/var/macports/build/_opt_local_var_macports_sources_svn.macports.org_trunk_dports_math_arpack/work/ARPACK && /usr/bin/ld -arch x86_64 -dynamic -dylib -single_module -dead_strip -x -all_load -L. -L/opt/local/lib/gcc45/x86_64 -L/opt/local/lib/gcc45 -L/opt/local/lib -dylib_install_name /opt/local/lib/libarpack.1.dylib -current_version 1 -compatibility_version 1 libarpack.a -o libarpack.1.dylib -latlas -llapack -lgfortran -lSystem" returned error 1

I'm attaching a patch

[mamoll (Mark Moll)]

Committed in r68541.