I see several people (like me) posting about missing lib*.la files while
compiling packages.  I finally figured out where these errors come from.

In my particular case I was 'missing' libpthread.la, which is not a
libtool-controlled library unless you have the 'pth' package installed,
in which case you have several libpthread libraries in /usr/pkg/lib,
including libpthread.la.

Well I once had the 'pth' package installed, during which time I must
have compiled the ORBit2 package.  After that I pkg_deleted the 'pth'
package, which removed libpthread.la (my 'missing' file).

However, there are still two other libtool files which reference the
'missing' file:  libORBit-2.la and libORBitCosNaming-2.la.  It seems
the ORBit2 package should have been recompiled when the 'pth' package
was deleted.

How to solve that dependency problem is beyond me, but maybe someone
else will know.

Anyway, to find the source of your 'missing' .la file just grep thru
all the other .la files in /usr/pkg/ for the name of your missing
file.  When you figure out which are the offending ones just re-
compile those packages which will regenerate the correct .la files
for you.