mergerfs: add missing patch

srcpkgs/mergerfs/patches/system-fuse.patch

@@ -0,0 +1,14 @@
+--- Makefile.orig	2017-06-04 20:12:49.459463768 +0200
++++ Makefile	2017-06-04 20:14:04.535236799 +0200
+@@ -77,9 +77,8 @@ help:
+ 	@echo "usage: make"
+ 	@echo "make XATTR_AVAILABLE=0 - to build program without xattrs functionality (auto discovered otherwise)"
+ 
+-$(TARGET): src/version.hpp obj/obj-stamp libfuse/lib/.libs/libfuse.a $(OBJ)
+-	cd libfuse && make
+-	$(CXX) $(CFLAGS) $(OBJ) -o $@ libfuse/lib/.libs/libfuse.a -ldl $(LDFLAGS)
++$(TARGET): src/version.hpp obj/obj-stamp $(OBJ)
++	$(CXX) $(CFLAGS) $(OBJ) -o $@ -lfuse -ldl $(LDFLAGS)
+ 
+ mount.mergerfs: $(TARGET)
+ 	$(LN) -fs "$<" "$@"