config/os/gnu-linux/time.c parses /proc/cpuinfo to determine the cpu speed. On Linux/SPARC it tries to read "Cpu0Bogo". However current kernels no longer provide "Cpu0Bogo", "Cpu0ClkTck" should be used instead.
Here's the patch:
http://sources.gentoo.org/viewcvs.py/gentoo-x86/media-sound/jack-audio-connection-kit/files/jack-audio-connection-kit-sparc-cpuinfo.patch?hideattic=0&view=markup