Make 'Compressible' an overridable property

This is needed to allow the Android Go versions of modules
(com.google.android.go.*) to select a different compression toggle than
their non-Go (com.google.android.*) conterparts. go/go-updatability

Bug: 203024418
Test: Preloaded go variants on wembley, booted Android.
Change-Id: Ic96aff5fafb65fbd08e8a69d47c994532e27819e
Merged-In: Ic96aff5fafb65fbd08e8a69d47c994532e27819e
(cherry picked from commit 2c4a9637)