Add write_if_changed property to genrule

When "write_if_changed: true" is set, it will call restat for ninja.
With this option the output file will be copied only if it is changed.

Bug: 290130959
Test: ninja rule include "--write-if-changed"
Change-Id: I8bd77b43b22eb0115e0bdc73718b2d6997d92652