filename property is an optional property that specifies the name of the
installed file which is by default name of the module.
This will be used to APEXs to have ./etc/ld.config.txt files for their
own.
Test: m (prebuilt_etc_test.go added)
Change-Id: Ic8d0c0044c5bc2c6c33117fe2c19ef6ad75451a8
The property is similar to the ones for cc_*, where it can additionally
create a recovery variant of the module when used.
Bug: 112780007
Test: Build mke2fs.conf with `recovery_available: true`.
Test: `go test -run TestPrebuiltEtc`
Change-Id: Ia04360d00453fa1f80022301feb369514f5e2b0b