Use findstring to check MODULE_BUILD_FROM_SOURCE

Android 12 can have _compressed target
(e.g com.google.android.conscrypt_compressed),
changed function from `filter` to `findstring`

Same change applied to com.google.android.art checking

Also modify to check `true` value of the MODULE_BUILD_FROM_SOURCE
to filter out both unset variable and `false`

Test: adding one error code temporally, install prebuilt
  train, and check result with,without this fix

    MODULE_BUILD_FROM_SOURCE := true
  + $(error we are here, true $(PRODUCT_PACKAGES))
  endif

Bug: 197282276
Change-Id: I864ba1bb5da61ccc6b8576029ab6c569959b2c93