Fix portmididrv not working on Linux

[fredrb]

I tried usng portmididrv on Linux, and kept running into -lporttime: Not found issues when linking.

I'm on Fedora 38. I checked that I had all the dependencies installed and porttime.h was in the include path.

Seems like porttime is now a part of portmidi, so there is no -lporttime to be linked, -lportmidi should be used instead.

I tested this change by replacing the go dependency in my project for my fork, and I was able to use portmididrv without any issues

replace "gitlab.com/gomidi/midi/v2" v2.1.7 => /path/to/go/midi/v2