Replace system:System.framework imports with system:System

This makes the linker work for both macOS and iOS targets

core/os/os2/process_posix_darwin.odin

@@ -10,7 +10,7 @@ import "core:sys/posix"
 import "core:sys/unix"
 import "core:time"
 
-foreign import lib "system:System.framework"
+foreign import lib "system:System"
 
 foreign lib {
 	sysctl :: proc(

core/os/os_darwin.odin

@@ -1,8 +1,8 @@
 package os
 
 foreign import dl   "system:dl"
-foreign import libc "system:System.framework"
-foreign import pthread "system:System.framework"
+foreign import libc "system:System"
+foreign import pthread "system:System"
 
 import "base:runtime"
 import "core:strings"