build: fix weston-info CFLAGS

CC       clients/weston-info.o
clients/weston-info.c:31:28: fatal error: wayland-client.h: No such file or directory
compilation terminated.
make[1]: *** [clients/weston-info.o] Error 1

Only triggerable if libwayland is only in a custom prefix.

Fix by adding CLIENT_CFLAGS.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

Makefile.am

@@ -547,6 +547,7 @@ weston_info_SOURCES =				\
 	shared/os-compatibility.c		\
 	shared/os-compatibility.h
 weston_info_LDADD = $(WESTON_INFO_LIBS)
+weston_info_CFLAGS = $(AM_CFLAGS) $(CLIENT_CFLAGS)
 
 weston_desktop_shell_SOURCES = clients/desktop-shell.c
 nodist_weston_desktop_shell_SOURCES =			\