macOS: Remove obsolete -single_module flag.

Thanks to dundargoc. #1284

src/Makefile

@@ -323,13 +323,13 @@ ifeq (Darwin,$(TARGET_SYS))
   endif
   TARGET_STRIP+= -x
   TARGET_XCFLAGS+= -DLUAJIT_UNWIND_EXTERNAL
-  TARGET_XSHLDFLAGS= -dynamiclib -single_module -undefined dynamic_lookup -fPIC
+  TARGET_XSHLDFLAGS= -dynamiclib -undefined dynamic_lookup -fPIC
   TARGET_DYNXLDOPTS=
   TARGET_XSHLDFLAGS+= -install_name $(TARGET_DYLIBPATH) -compatibility_version $(MAJVER).$(MINVER) -current_version $(MAJVER).$(MINVER).255
 else
 ifeq (iOS,$(TARGET_SYS))
   TARGET_STRIP+= -x
-  TARGET_XSHLDFLAGS= -dynamiclib -single_module -undefined dynamic_lookup -fPIC
+  TARGET_XSHLDFLAGS= -dynamiclib -undefined dynamic_lookup -fPIC
   TARGET_DYNXLDOPTS=
   TARGET_XSHLDFLAGS+= -install_name $(TARGET_DYLIBPATH) -compatibility_version $(MAJVER).$(MINVER) -current_version $(MAJVER).$(MINVER).255
   ifeq (arm64,$(TARGET_LJARCH))