Add dependency on dexpreopt.config to soong_build doc generation. am: ebb0b574c8 am: 3c3ad6a444 am: d249069c7c

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1483797

Change-Id: Iad0fb45b26cb98fcb2143826df67d463c76b0d8a