pipewire.conf.in: use absolute path to pipewire-media-session

So pipewire daemon is able to find pipewire-media-session from the
location it's installed to, even when it's not in $PATH.

For the `pw-ininstalled.sh` and `make run` invocations, provide a
`src/daemon/pipewire-uninstalled.conf` that still uses the relative
path, but isn't installed.

Makefile.in

@@ -14,7 +14,7 @@ run: all
 	SPA_PLUGIN_DIR=@BUILD_ROOT@/spa/plugins \
 	PIPEWIRE_MODULE_DIR=@BUILD_ROOT@ \
 	PATH=@BUILD_ROOT@/src/examples:$(PATH) \
-	PIPEWIRE_CONFIG_FILE=@BUILD_ROOT@/src/daemon/pipewire.conf \
+	PIPEWIRE_CONFIG_FILE=@BUILD_ROOT@/src/daemon/pipewire-uninstalled.conf \
 	$(DBG) @BUILD_ROOT@/src/daemon/pipewire
 
 gdb:

pw-uninstalled.sh

@@ -31,7 +31,7 @@ if [ ! -d ${BUILDDIR} ]; then
 	exit -1
 fi
 
-export PIPEWIRE_CONFIG_FILE="${BUILDDIR}/src/daemon/pipewire.conf"
+export PIPEWIRE_CONFIG_FILE="${BUILDDIR}/src/daemon/pipewire-uninstalled.conf"
 export SPA_PLUGIN_DIR="${BUILDDIR}/spa/plugins"
 export PIPEWIRE_MODULE_DIR="${BUILDDIR}/src/modules"
 export PATH="${BUILDDIR}/src/daemon:${BUILDDIR}/src/tools:${BUILDDIR}/src/examples:${PATH}"

src/daemon/meson.build

@@ -17,13 +17,20 @@ pipewire_c_args = [
 
 conf_config = configuration_data()
 conf_config.set('VERSION', '"@0@"'.format(pipewire_version))
+conf_config.set('media_session_path', pipewire_bindir / 'pipewire-media-session')
 conf_install_dir = join_paths(get_option('sysconfdir'), 'pipewire')
 
+conf_config_uninstalled = conf_config
+conf_config_uninstalled.set('media_session_path', 'pipewire-media-session')
+
 configure_file(input : 'pipewire.conf.in',
                output : 'pipewire.conf',
                configuration : conf_config,
                install_dir : conf_install_dir)
 
+configure_file(input : 'pipewire.conf.in',
+               output : 'pipewire-uninstalled.conf',
+               configuration : conf_config)
 
 executable('pipewire',
   pipewire_daemon_sources,

src/daemon/pipewire.conf.in

@@ -74,4 +74,4 @@ create-object spa-node-factory factory.name=support.node.driver node.name=Dummy
 # Execute the given program. This is usually used to start the
 # session manager. run the session manager with -h for options
 #
-exec pipewire-media-session # -d alsa-seq,alsa-pcm,bluez5,metadata
+exec @media_session_path@ # -d alsa-seq,alsa-pcm,bluez5,metadata