Fix build with musl libc

[ebfe]

CCEQ is not available under musl libc.

[mptre]

Thanks for the PR. I'd rather just inline the macro then, please try out
#250 and let me know if it works.

I'm trying to build with musl on Travis but ran into some issues. How
are you compiling pick with musl? Is anything more than the commands
below necessary? Travis uses Ubuntu and I did install the musl-tools
package.

$ env CC=musl-gcc ./configure
$ make

[ebfe]

#250 is fine too. I'm building on a Void Linux system with musl as the system libc. No other changes necessary here.

[mptre]

Great, merged.

Are you packaging pick for Void Linux? If true, consider submitting a PR
with install instructions added to the README.