Allow uninstallable linker_config to be packaged

Till now, linker_config has to be installable to be packaged. With this
commit, packaging modules like filesystem now can include uninstallable
linker_config. This can help when linker_config can conflict with other
partitions e.g. system.

Bug: 185391776
Test: build filesystem with uninstallable linker_config
Change-Id: Ic2cece08be73749e6bd1f813152c67f8e3904c20