Log Message:
Update pkg_comp to 1.38nb1

pkgsrc uses the "BUILD_TARGET" definition internally as the primary
target for building in a package's WRKDIR.  It defaults to "all".
So pkgsrc cd's to ${WRKDIR} and does a "make ${BUILD_TARGET}"

pkg_comp also wants to use the same "BUILD_TARGET" definition
internally for itself to guide the builds for making binary packages.
It's done at a higher level than the pkgsrc definition.  It defaults
to "package".

The use of the same name for two different purposes can cause
pkg_comp to fail to build packages. This commit renames the pkg_comp
definition to be "BUILD_PKG_COMP_TARGET".

With this change in place, my pkg_comp builds now complete successfully.

Bump PKGREVISION for the BUILD_PKG_COMP_TARGET fix