Fix 'errno undeclared' compile error with older gcc versions

alsa-project/alsa-gobject pull request #83 was opened from michele-perrone:

It looks like errno.h has to be included explicitly when compiling with older gcc versions. This issue was encountered on the following system: - Ubuntu 20.04 LTS - Linux 5.4.0-156 - gcc 10.5.0 - Meson 0.53.2

Request URL : https://github.com/alsa-project/alsa-gobject/pull/83 Patch URL : https://github.com/alsa-project/alsa-gobject/pull/83.patch Repository URL: https://github.com/alsa-project/alsa-gobject