bug in aclocal.m4

[Evan Laforge]

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".