meson: generate pkg-config -uninstalled pc files

Generating those files is useful for users building the GStreamer stack
using meson and having to link it to another project which is still
using the autotools.

https://bugzilla.gnome.org/show_bug.cgi?id=776810

pkgconfig/Makefile.am

@@ -10,7 +10,11 @@ all-local: $(pcfiles) $(pcfiles_uninstalled)
 %-@GST_API_VERSION@.pc: %.pc
 	cp $< $@
 %-@GST_API_VERSION@-uninstalled.pc: %-uninstalled.pc
-	cp $< $@
+### the uninstalled libdir is depend of the build system used so set it here
+### rather than hardcoding it in the file directly.
+	$(AM_V_GEN) sed \
+		-e "s|[@]rtspserverlibdir[@]|$(abs_top_builddir)/gst/rtsp-server/.libs|" \
+		$< > $@.tmp && mv $@.tmp $@
 
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = $(pcfiles)

pkgconfig/gstreamer-rtsp-server-uninstalled.pc.in

@@ -1,7 +1,7 @@
 # the standard variables don't make sense for an uninstalled copy
 prefix=
 exec_prefix=
-libdir=@abs_top_builddir@/gst/rtsp-server/.libs
+libdir=@rtspserverlibdir@
 includedir=@abs_top_builddir@
 
 Name: gst-rtsp-server

pkgconfig/meson.build

@@ -7,11 +7,21 @@ pkgconf.set('includedir', '${prefix}/@0@'.format(get_option('includedir')))
 pkgconf.set('GST_API_VERSION', api_version)
 pkgconf.set('VERSION', gst_version)
 
+# needed for generating -uninstalled.pc files
+pkgconf.set('abs_top_builddir', join_paths(meson.current_build_dir(), '..'))
+pkgconf.set('abs_top_srcdir', join_paths(meson.current_source_dir(), '..'))
+pkgconf.set('rtspserverlibdir', join_paths(meson.build_root(), gst_rtsp_server.outdir()))
+
 pkg_install_dir = '@0@/pkgconfig'.format(get_option('libdir'))
 
-# FIXME: -uninstalled.pc files (if still needed?)
 configure_file(input : 'gstreamer-rtsp-server.pc.in',
   output : 'gstreamer-rtsp-server-1.0.pc',
   configuration : pkgconf,
   install_dir : pkg_install_dir,
 )
+
+configure_file(input : 'gstreamer-rtsp-server-uninstalled.pc.in',
+  output : 'gstreamer-rtsp-server-1.0-uninstalled.pc',
+  configuration : pkgconf,
+  install_dir : pkg_install_dir
+)