bug in aclocal.m4

Tiny bug, so I'll just throw it out here instead of trying to get arc set up again: aclocal.m4 line 2438, at head (commit 7e77f41430ae1cad84d5b0c90328331d38f3eda0) has # typo'd as $. It causes a harmless but alarming error in configure. Also `ld --version` causes an error on OS X since OS X ld doesn't have that flag, but I think it just causes it to correctly detect it as "not gnu ld".