[Ur] problems building Ur/Web on OS X since the change to dynamic so libs

[Adam Chlipala]

Georg Bauer wrote:
> libtool --mode=compile gcc -Wimplicit -O3 -I include -c src/c/memmem.c
> -o lib/c/memmem.lo
> libtool: unknown option character `-' in: --mode=compile....
>    

OK, it looks like OSX has its own version with different syntax from GNU 
libtool.  Does anyone have a suggestion as to what should go in 
Makefile.in instead?