Building libdv-1.0.0 on x86_64-sun-solaris2.10 (not OpenSolaris) with the no-cost Sun/Oracle Workshop 12.2 compiler toolchain.
Although all the pthread-related stuff is in libpthread and is correctly being detected by configure, on Solaris the sched_* functions are in the "realtime" library, librt. The simple fix is to check for sched_setscheduler in -lrt after checking for libpthread.
Here's what configure now outputs for me:
checking for pthread_create in -lpthread... yes
checking for sqrt in -lm... yes
checking for sched_setscheduler in -lrt... yes
Simple patch is attached.