Move image mutator things to image.go

Bug: N/A
Test: m
Change-Id: I2d1a24fc067c376ed2e0741313d48248ad78ee78
diff --git a/cc/Android.bp b/cc/Android.bp
index 9ece05f..831911e 100644
--- a/cc/Android.bp
+++ b/cc/Android.bp
@@ -19,6 +19,7 @@
         "check.go",
         "coverage.go",
         "gen.go",
+        "image.go",
         "linkable.go",
         "lto.go",
         "makevars.go",