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.

diff --git a/magick/GraphicsMagick.pc.in b/magick/GraphicsMagick.pc.in
index 5757b37..87e3fd4 100644
--- a/magick/GraphicsMagick.pc.in
+++ b/magick/GraphicsMagick.pc.in
@@ -8,4 +8,6 @@ Name: GraphicsMagick
 Version: @PACKAGE_VERSION@
 Description: GraphicsMagick image processing library
+Requires.private: libxml-2.0
 Libs: -L${libdir} -lGraphicsMagick
+Libs.private: @MAGICK_API_LDFLAGS@ @MAGICK_API_LIBS@
 Cflags: -I${includedir} @MAGICK_API_PC_CPPFLAGS@