The PLATFORM variable is assigned either from $ANDROID_PLATFORM or gets
a default value (currently $PLATFORM_VERSION).
The check to use either dx (SDK < 31) or d8 (SDK >= 31) must be based on
the actual $PLATFORM, not the default $PLATFORM_VERSION.
Refs 52138fd921
Refs <https://salsa.debian.org/yangfl-guest/scrcpy/-/blob/57d30780dd38b9641992a873d760ac0f4bc3a387/debian/patches/0002-Workaround-broken-script.patch>
PR #2850 <https://github.com/Genymobile/scrcpy/pull/2850>
Signed-off-by: Romain Vimont <rom@rom1v.com>