USES=pathfix broken?

[Don Lewis]

I've started getting a bunch of pkg-fallout@ email reporting missing
libdata/pkgconfig/*.pc files.  It looks like the *.pc files are getting
installed under lib/pkgconfig.

[snip]
 /bin/mkdir -p '/wrkdirs/usr/ports/devel/mtbl/work/stage/usr/local/lib/pkgconfig'
 install  -m 0644 mtbl/libmtbl.pc '/wrkdirs/usr/ports/devel/mtbl/work/stage/usr/local/lib/pkgconfig'
[snip]
===>  Building package for mtbl-0.8.0
pkg-static: Unable to access file /wrkdirs/usr/ports/devel/mtbl/work/stage/usr/local/libdata/pkgconfig/libmtbl.pc: No such file or directory
[snip]

So far the problems have been with limited to
[package - head-amd64-default] and
[exp - 103i386-default-build-as-user].  The latter would seem to
eliminate the recent sed changes in -CURRENT as a cause.  I'm not seeing
any problems with the r432015 revision of the ports tree, and I don't
see any suspicious commits to ports/Mk after that point.