rosegarden FTBFS in 64-bit

Slackware Current 64-bit The failure: /usr/lib64/gcc/x86_64-slackware-linux/4.7.1/../../../../x86_64-slackware-linux/bin/ld: CMakeFiles/rosegardensequencer.dir/sequencer/main.cpp.o: undefined reference to symbol 'pthread_sigmask@@GLIBC_2.2.5' /usr/lib64/gcc/x86_64-slackware-linux/4.7.1/../../../../x86_64-slackware-linux/bin/ld: note: 'pthread_sigmask@@GLIBC_2.2.5' is defined in DSO /lib64/libpthread.so.0 so try adding it to the linker command line /lib64/libpthread.so.0: could not read symbols: Invalid operation collect2: error: ld returned 1 exit status rosegarden builds without that error in 32-bit. How to fix? Darrell