Add pom2mk -regen

pom2mk -regen Android.mk will read the previous arguments out of
Android.mk, rerun pom2mk with those arguments, and write the result
to Android.mk.

Bug: 78300023
Test: cd prebuilts/sdk/current/support && pom2mk -regen Android.mk
Change-Id: Ie8e0f97ae5b87c8078cf8e753489326d80da1896
Merged-In: Ie8e0f97ae5b87c8078cf8e753489326d80da1896
(manually cherry-picked from 6b359adc1e2bf1726567000d97e412fea6e88b95)