Use mkdir -p instead of ignoring return code

We want `make` to fail if the directory doesn't exist and can't be
made for some reason.

Makefile

@@ -32,14 +32,14 @@ else
 endif
 
 all:
-	-mkdir bin
+	mkdir -p bin
 	cp scripts/keyd-application-mapper bin/
 	sed -e 's#@PREFIX@#$(PREFIX)#' keyd.service.in > keyd.service
 	$(CC) $(CFLAGS) -O3 $(COMPAT_FILES) src/*.c src/vkbd/$(VKBD).c -lpthread -o bin/keyd $(LDFLAGS)
 debug:
 	CFLAGS="-g -Wunused" $(MAKE)
 compose:
-	-mkdir data
+	mkdir -p data
 	./scripts/generate_xcompose
 man:
 	for f in docs/*.scdoc; do \
@@ -96,7 +96,7 @@ test:
 		./$$f; \
 	done
 test-io:
-	-mkdir bin
+	mkdir -p bin
 	$(CC) \
 	-DDATA_DIR= \
 	-o bin/test-io \