Fix an issue where updating a `zephyr_code_relocate()` call in CMake
didn't trigger regeneration of `code_relocation.c` and linker scripts.
The generation command was missing a dependency on the aforementioned
input text file, where the outcome of each call is cached.
Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>