Sorry...
I'm stupid.

$ ruby extconf.rb --with-pgsql-include-dir=/usr/local/pgsql/include \
                  --with-pgsql-lib-dir=/usr/local/pgsql/lib \
		  --with-pgsql-srcinc-dir=/usr/local/src/postgresql-7.1/src/include/ \
                  --with-pgsql-version=71 \
                  --enable-shared
                  ~~~~~~~~~~~~~~~~~~

checking for catalog/pg_proc.h... yes
checking for PQsetdbLogin() in -lpq... yes
creating Makefile

$ make
$ make test
(cd test/plt ; ./runtest 71)
**** Destroy old database plruby_test ****
DROP DATABASE
**** Create test database plruby_test ****
CREATE DATABASE
**** Create procedural language plruby ****
**** Create tables, functions and triggers ****
**** Running test queries ****
    Tests passed O.K.
(cd test/plp ; ./runtest 71)
**** Destroy old database plruby_test ****
DROP DATABASE
**** Create test database plruby_test ****
CREATE DATABASE
**** Create procedural language plruby ****
**** Create tables, functions and triggers ****
**** Running test queries ****
    Tests passed O.K.



From: Noboru Saitou <noborus / ZetaBITS.com>

> Hi, 
> I'm trying plruby compile.
> 
> My platfrorm.
> Debian GNU Linux
> Linux 2.2.18pre21 i586
> 
> PostgreSQL-7.1
> Ruby-1.6.4preview2
> 
> plruby-0.2.2
> 
> $ ruby extconf.rb --with-pgsql-include-dir=/usr/local/pgsql/include \
>                   --with-pgsql-lib-dir=/usr/local/pgsql/lib \
> 		  --with-pgsql-srcinc-dir=/usr/local/src/postgresql-7.1/src/include/ \
>                   --with-pgsql-version=71 
> 
> $ make
> gcc -fPIC -g -O2 -I/usr/local/src/postgresql-7.1/src/include/ -I/usr/local/pgsql/include -DPG_PL_VERSION=71 -I/usr/local/lib/ruby/1.6/i586-linux -I/usr/local/include -DHAVE_CATALOG_PG_PROC_H   -c -o plruby.o plruby.c
> gcc -shared  -L/usr/local/lib/ruby/1.6/i586-linux -L/usr/local/lib  -L/usr/local/pgsql/lib -o plruby.so plruby.o  -lruby -lpq -lc 
> 
> $ make test
> (cd test/plt ; ./runtest 71)
> **** Destroy old database plruby_test ****
> DROP DATABASE
> **** Create test database plruby_test ****
> CREATE DATABASE
> **** Create procedural language plruby ****
> **** Create tables, functions and triggers ****
> **** Running test queries ****
>     Tests faild - look at diffs between
>     test.expected.71 and test.out

(snip)