configure tests link against the wrong libraries on AMD64

[atsampson]

When building on an AMD64 machine, KRoC cross-builds for IA32 -- i.e. it passes -m32 to GCC and winds up linking against 32-bit libraries. However, the configure tests that check for libraries don't ever find out about the extra linker flags, so they check for the AMD64 libraries. As a result, you can wind up getting modules enabled that can't possibly build.

The problem is that occbuild and occbuild.m4 only exposes CFLAGS for native code, not linker flags. This could be fixed by adding a --libs flag to occbuild, and have occbuild.m4 export the result as OCCBUILD_LIBS (both names by analogy with pkg-config), which could then be used when doing configure tests for native libraries.