intl dep: forward static to iconv if needed

In 1fb6c93947 the intl dep gained support for static linking
which also forwarded this property to the iconv sub dependency.

The refactoring in 214d03568f lost this change, which results in
iconv getting linked dynamically again.

Forward static again to fix this.

mesonbuild/dependencies/misc.py

@@ -487,7 +487,7 @@ class IntlSystemDependency(SystemDependency):
             self.is_found = True
 
             if self.static:
-                if not self._add_sub_dependency(iconv_factory(env, self.for_machine, {})):
+                if not self._add_sub_dependency(iconv_factory(env, self.for_machine, {'static': True})):
                     self.is_found = False
                     return