meson: dep fix for compositor.h needing xkbcommon.h

This fixes:

[    5s] cc -Ilibweston/2b98b6d@@session-helper@sta -Ilibweston -I../libweston -Ilibweston/.. -I../libweston/.. -Ilibwes
ton/../shared -I../libweston/../shared -I/usr/include/pixman-1 -I/usr/include/libdrm -I/usr/include/dbus-1.0 -I/usr/lib6
4/dbus-1.0/include -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -std=gnu99 -Wno-unused-parameter -Wno-shift-n
egative-value -Wno-missing-field-initializers -fvisibility=hidden -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong
 -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g -fPIC  -MD -MQ 'libweston/2b98b6d@@session-hel
per@sta/launcher-util.c.o' -MF 'libweston/2b98b6d@@session-helper@sta/launcher-util.c.o.d' -o 'libweston/2b98b6d@@sessio
n-helper@sta/launcher-util.c.o' -c ../libweston/launcher-util.c
[    5s] In file included from ../libweston/launcher-util.c:29:
[    5s] ../libweston/compositor.h:39:10: fatal error: xkbcommon/xkbcommon.h: No such file or directory
[    5s]  #include <xkbcommon/xkbcommon.h>

For completeness, also add the same for wayland-server.h.

Reported-by: Jan Engelhardt <jengelh@inai.de>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

libweston/meson.build

@@ -121,7 +121,11 @@ srcs_session_helper = [
 ]
 deps_session_helper = [
 	# for compositor.h needing pixman.h
-	dep_pixman.partial_dependency(compile_args: true)
+	dep_pixman.partial_dependency(compile_args: true),
+	# for compositor.h needing xkbcommon.h
+	dep_xkbcommon.partial_dependency(compile_args: true),
+	# for compositor.h needing wayland-server.h
+	dep_wayland_server.partial_dependency(compile_args: true)
 ]
 
 if get_option('backend-drm')