build: scope IBus flags, rebuild containers with clean, dedup gtk install

Only ibus.o needs the D-Bus and xkbcommon flags, so give them the same
per-object scoping as the popup and XIM objects. The docker targets used
-B, which recursive makes inherit: the daemon was linked three times and
the live tests built twice per docker-check. gtk/Makefile repeated the
module-directory check and cache refresh in install and uninstall.

gtk/Makefile

@@ -21,30 +21,20 @@ $(PROG): main.c ../ipc.c ../ipc.h
 	$(CC) $(CPPFLAGS) -I.. $(GTK_CFLAGS) -Wall $(CFLAGS) $(LDFLAGS) \
 		-shared -fPIC -o $@ main.c ../ipc.c $(GTK_LIBS) $(LDLIBS)
 
+CHECKDIR = test -n "$$module_dir" || { \
+	echo "cannot find GTK 3 module directory; set GTK_MODULE_DIR" >&2; \
+	exit 1; }
+REFRESH = test -n "$(DESTDIR)" || { \
+	unset GTK_PATH GTK_IM_MODULE_FILE; $(GTK_QUERY_IMMODULES) --update-cache; }
+
 install: $(PROG)
-	module_dir="$(GTK_MODULE_DIR)"; \
-	test -n "$$module_dir" || { \
-		echo "cannot find GTK 3 module directory; set GTK_MODULE_DIR" >&2; \
-		exit 1; \
-	}; \
+	module_dir="$(GTK_MODULE_DIR)"; $(CHECKDIR); \
 	mkdir -p "$(DESTDIR)$$module_dir" && \
-	cp "$(PROG)" "$(DESTDIR)$$module_dir/" && \
-	if test -z "$(DESTDIR)"; then \
-		unset GTK_PATH GTK_IM_MODULE_FILE; \
-		$(GTK_QUERY_IMMODULES) --update-cache; \
-	fi
+	cp "$(PROG)" "$(DESTDIR)$$module_dir/" && $(REFRESH)
 
 uninstall:
-	module_dir="$(GTK_MODULE_DIR)"; \
-	test -n "$$module_dir" || { \
-		echo "cannot find GTK 3 module directory; set GTK_MODULE_DIR" >&2; \
-		exit 1; \
-	}; \
-	rm -f "$(DESTDIR)$$module_dir/$(PROG)" && \
-	if test -z "$(DESTDIR)"; then \
-		unset GTK_PATH GTK_IM_MODULE_FILE; \
-		$(GTK_QUERY_IMMODULES) --update-cache; \
-	fi
+	module_dir="$(GTK_MODULE_DIR)"; $(CHECKDIR); \
+	rm -f "$(DESTDIR)$$module_dir/$(PROG)" && $(REFRESH)
 
 clean:
 	rm -f $(PROG)