debian/lalsuite.mk: Lack of Octave not handled properly (all LALsuite components)

If (as required for Bullseye after their transition to Octave 6.x which is no longer supported by SWIG) Octave isn't provided, e.g. by removing liboctave-dev from Build-Depends:, the "configure" stage fails due to not finding octave. IMHO this can be handled by conditionally adding --disable-swig-octave to the configure line the same way it's already done for the "build" stage - if HAVE_OCTAVE isn't defined.

As suggested in https://git.ligo.org/sccb/requests/-/issues/634#note_244044,

diff -Nur old/debian/lalsuite.mk new/debian/lalsuite.mk
--- old/debian/lalsuite.mk      2021-02-11 02:06:07.000000000 +0100
+++ new/debian/lalsuite.mk      2021-02-24 14:25:24.000000000 +0100
@@ -33,6 +33,7 @@
        # configure the build for the 'main' python version
        dh_auto_configure -- \
                --disable-gcc-flags \
+               --disable-swig-octave $(if $(WITH_OCTAVE),--enable-swig-octave) \
                $(CONFIGUREARGS) \
                PYTHON=$(PYTHON)

does the trick, but the must be a cleaner-looking way that avoids enabling after disabling. Anyone?

(Is there a reason why the "build" stage always uses --disable-swig-octave?)