ogra@anubis:~/Devel/packages/help2man-1.47.3$ gcc -o bindtextdomain.so -fPIC -shared bindtextdomain.c -ldl
ogra@anubis:~/Devel/packages/help2man-1.47.3$ export LD_PRELOAD=./bindtextdomain.so
ogra@anubis:~/Devel/packages/help2man-1.47.3$ export TEXTDOMAIN=foobar
ogra@anubis:~/Devel/packages/help2man-1.47.3$ export LOCALEDIR=moo
ogra@anubis:~/Devel/packages/help2man-1.47.3$ strace -f gettext file-roller 2>&1 | grep \\.mo
open("/home/ogra/Devel/packages/help2man-1.47.3/moo/de_DE/LC_MESSAGES/foobar.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/home/ogra/Devel/packages/help2man-1.47.3/moo/de/LC_MESSAGES/foobar.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale-langpack/de_DE/LC_MESSAGES/foobar.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale-langpack/de/LC_MESSAGES/foobar.mo", O_RDONLY) = -1 ENOENT (No such file or directory)