Strip my_shared_libraries to remove space char

This commit strips my_shared_libraries to remove the unwanted space
character when both `$(filter-out ...)` and
`$(my_system_shared_libraries)` are empty.

Bug: 137302468
Test: lunch aosp_walleye-userdebug && make
Test: lunch aosp_walleye-userdebug && make check-elf-files
Change-Id: Ia0410da877196c104a61d48c92a2be969a9754a5