Add build rule for build-octave (bug #49503). * src/build-octave.mk: Add new build rule for build-octave which can be used for cross-building binary packages that depend on Octave as a build tool. * dist-files.mk: Add new file to list. * index.html: Add new package to list. * src/of-communications.mk, src/of-image.mk, src/of-mapping.mk, src/of-optiminterp.mk, src/of-sparsersb.mk, src/of-statistics.mk, src/of-windows.mk: Add optional dependency on build-octave. * configure.ac: Add new configure switch "--disable-system-octave" that is needed to build the build-octave package. * Makefile.in: Add variable "USE_SYSTEM_OCTAVE". Exclude build-octave from the default build tools and build it only if a package explicitly depends on it. Display warning about missing native Octave version only if necessary.

# This file is part of MXE.
# See index.html for further information.

PKG             := xz
$(PKG)_IGNORE   :=
$(PKG)_VERSION  := 5.2.5
$(PKG)_CHECKSUM := 0b9d1e06b59f7fe0796afe1d93851b9306b4a3b6
$(PKG)_SUBDIR   := $(PKG)-$($(PKG)_VERSION)
$(PKG)_FILE     := $(PKG)-$($(PKG)_VERSION).tar.xz
$(PKG)_URL      := http://tukaani.org/xz/$($(PKG)_FILE)
$(PKG)_DEPS     :=

define $(PKG)_UPDATE
    $(WGET) -q -O- 'http://tukaani.org/xz/' | \
    $(SED) -n 's,.*xz-\([0-9][^>]*\)\.tar.*,\1,p' | \
    head -1
endef

define $(PKG)_BUILD
    cd '$(1)' && ./configure \
        $(HOST_AND_BUILD_CONFIGURE_OPTIONS) \
        --prefix='$(HOST_PREFIX)' \
        $(ENABLE_SHARED_OR_STATIC) \
        --disable-threads \
        --disable-nls
    $(MAKE) -C '$(1)'/src/liblzma -j '$(JOBS)' install DESTDIR='$(3)'
endef