remove binary before copying to destination

Since Linux 6.11 is possible overwrite a running executable, possibly making it
crash.

Thanks to: movq42rax
Fixes: https://codeberg.org/dwl/dwl/issues/709
References: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2a010c412853
References: https://lore.kernel.org/stable/CACKH++YAtEMYu2nTLUyfmxZoGO37fqogKMDkBpddmNaz5HE6ng@mail.gmail.com/T/#u

(cherry picked from commit 1d08ade132)

Makefile

@@ -61,6 +61,7 @@ dist: clean
 
 install: dwl
 	mkdir -p $(DESTDIR)$(PREFIX)/bin
+	rm -f $(DESTDIR)$(PREFIX)/bin/dwl
 	cp -f dwl $(DESTDIR)$(PREFIX)/bin
 	chmod 755 $(DESTDIR)$(PREFIX)/bin/dwl
 	mkdir -p $(DESTDIR)$(MANDIR)/man1

dwl.c

@@ -1177,7 +1177,6 @@ void
 destroydecoration(struct wl_listener *listener, void *data)
 {
 	Client *c = wl_container_of(listener, c, destroy_decoration);
-	c->decoration = NULL;
 
 	wl_list_remove(&c->destroy_decoration.link);
 	wl_list_remove(&c->set_decoration_mode.link);
@@ -3143,7 +3142,7 @@ sethints(struct wl_listener *listener, void *data)
 {
 	Client *c = wl_container_of(listener, c, set_hints);
 	struct wlr_surface *surface = client_surface(c);
-	if (c == focustop(selmon))
+	if (c == focustop(selmon) || !c->surface.xwayland->hints)
 		return;
 
 	c->isurgent = xcb_icccm_wm_hints_get_urgency(c->surface.xwayland->hints);