Support AllowMissingDependencies for apex dependencies

Use android.OutputFileForModule instead of cc.Module.OutputFile,
which will already handle the AllowMissingDependencies case.

Bug: 250918230
Test: lunch aosp_riscv64-userdebug && m ALLOW_MISSING_DEPENDENCIES=true nothing
Change-Id: I605ae9afe06ac450adec1d2a856e529e45ed5cb5