BUG #6198: init-po fails for plperl due to invalid xsubpp path (contains ExtUtils)

The following bug has been logged online:

Bug reference: 6198
Logged by: init-po fails for plperl due to invalid xsubpp path
Email address: tv(at)fuzzy(dot)cz
PostgreSQL version: 9.0.4, 9.1-rc1
Operating system: Linux
Description: init-po fails for plperl due to invalid xsubpp path
(contains ExtUtils)
Details:

When I try to prepare a fresh .pot file for plpgsql, it fails like this

$ ./configure --enable-nls=cs
$ cd src/pl/plperl
$ gmake init-po
'/usr/bin/perl' /ExtUtils/xsubpp -typemap /ExtUtils/typemap SPI.xs >SPI.c
Can't open perl script "/ExtUtils/xsubpp": Directory or file does not
exist.
gmake: *** [SPI.c] Error 2
gmake: *** Deleting file `SPI.c'

This is due to invalid xsubpp/typemap paths - the xsubpp is available here

$ which xsubpp
/usr/bin/xsubpp

but the GNUmakefile contains this:

$(PERL) $(perl_privlibexp)/ExtUtils/xsubpp -typemap
$(perl_privlibexp)/ExtUtils/typemap $< >$@

After changing to

xsubpp -typemap
/usr/src/linux-2.6.38-gentoo-r6/tools/perf/scripts/perl/Perf-Trace-Util/type
map $< >$@

it works fine.