Based on
https://github.com/qbbr/dwm and dwm-6.1-systray.diff from
http://http://dwm.suckless.org/patches/systray the problem might be that you need to comment out line 21
Code:
FREETYPEINC = ${X11INC}/freetype2
in your config.mk because according to your profile you're using linux, not BSD. (According to the comment in line 20, that line is for BSD
only. Bad pitfall, that. Should be solved by some automatic makefile creation, really.)
If that doesn't help, you'll have to provide more information on where you got the diff and code from and what you've changed so far.
PS: If you're compiling things regularly, you might want to read up on makefiles a bit more.