pthread mutex error building 6.10 on NetBSD

[Donn Cave]

I tried to build GHC 6.10.1 on NetBSD 4.0 this afternoon, and ran into
an error, where cabal-bin calls the stage2 ghc in utils/installPackage.

pthread_mutex_unlock() is called, evidently from fileLock(), with an
invalid mutex.

NetBSD's pthread implementation differs from Linux in its intolerance
of such things.  I have found errors where someone forgets that a mutex
was never used and tries to unlock it.  I guess you could do that all day
long on Linux without noticing anything, but NetBSD aborts the program.
In the present case, I don't see anything like that wrong in rts/FileLock.c,
though.  I'm stumped.

So I'm checking, has anyone else built 6.10 on NetBSD?

	Donn