Add restat = 1 to Swift compile rule

The swift compiler does not update the modification time of output
object files when the code has not changed. Without this, Swift
targets may continuously be rebuilt.

mesonbuild/backend/ninjabackend.py

@@ -2449,7 +2449,7 @@ class NinjaBackend(backends.Backend):
 
         command = invoc + ['$ARGS', '$in']
         description = 'Compiling Swift source $in'
-        self.add_rule(NinjaRule(rule, command, [], description))
+        self.add_rule(NinjaRule(rule, command, [], description, extra='restat = 1'))
 
     def use_dyndeps_for_fortran(self) -> bool:
         '''Use the new Ninja feature for scanning dependencies during build,