Linux Mint Xapp missing library package fix

Errors

Some errors which I encountered during building 'systray' (github.com/getlantern/systray¹)

Package xapp was not found in the pkg-config search path.
Perhaps you should add the directory containing `xapp.pc'
to the PKG_CONFIG_PATH environment variable
running gcc failed: exit status 1
/usr/bin/ld: cannot find -lxapp
collect2: error: ld returned 1 exit status

Solution

Simply install the missing² package with

sudo apt-get install libxapp-dev