klystrack: ftbfs with GCC-10

[alexmyczko]

Please see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=957407

[izobilje]

Compiling on Arch with GCC 10.1.0, there are many "multiple definition" errors. As seen here, either the source should be fixed, or, as a workaround, -fcommon can be added to the CFLAGS in Makefile.