Fix ALLOW_MISSING_DEPENDENCIES in PDK builds

ALLOW_MISSING_DEPENDENCIES was being set up before TARGET_BUILD_PDK, so
PDK builds were not triggering ALLOW_MISSING_DEPENDENCIES.

Bug: 62086238
Test: m -j nothing (check out/soong/soong.variables for AllowMissingDependencies)
Test: PDK_FUSION_PLATFORM_ZIP=test.zip m -j nothing (check AllowMissingDependencies)
Change-Id: I70919fbc7e397e55356cb467c6218cf6e7279c6c
2 files changed