multimedia/libass: CONFIGURE_ARGS depends on whether sources were extracted

[Aleksey Cheusov <vle%gmx.net@localhost>]

The following type script demonstrates the problem:

libass$ make clean 2>/dev/null 1>&2; make show-var VARNAME=CONFIGURE_ARGS; make extract 2>/dev/null >&2; make show-var VARNAME=CONFIGURE_ARGS
--disable-asm --x-includes=/usr/X11R7/include --x-libraries=/usr/X11R7/lib --prefix=/usr/pkg --build=x86_64--netbsd --host=x86_64--netbsd --mandir=/usr/pkg/man --enable-option-checking=yes
--disable-asm --prefix=/usr/pkg --build=x86_64--netbsd --host=x86_64--netbsd --mandir=/usr/pkg/man --enable-option-checking=yes
libass$

X11_TYPE is native.
Obviously, this results to build failure if we run "make extract" before "make configure".

Ideas?