mxcl/homebrew — pull request #9802 by chrisko (2012-01-27 05:07:11+00:00)
Title: sox: reference libpng in build to enable spectrogram effect

SoX has an optional "spectrogram" effect ([doc](http://sox.git.sourceforge.net/git/gitweb.cgi?p=sox/sox;a=blob;f=sox.1;h=43f3583d24091e6996e9f08ae2722d428b0abc9a;hb=HEAD#l3083)) that's included whenever libpng is detected ([logic](http://sox.git.sourceforge.net/git/gitweb.cgi?p=sox/sox;a=blob;f=CMakeLists.txt;h=4c83823f3c69f8a2cffaa1797db0bec05d72c00c;hb=HEAD#l130)). Unlike some other formulas ([e.g.](https://github.com/mxcl/homebrew/blob/master/Library/Formula/pngnq.rb#L19)) the SoX formula doesn't reference `ENV.x11`, where OS X keeps libpng (cf. `brew install libpng`). This one line remedies that.

To test that it worked, run `sox --help | grep spectrogram | wc -l`. Should be 1.