Pedro Silva Ferreira improved build system reliability for the zephyrproject-rtos/poky repository by addressing a bug in the RUSTLIB path override mechanism. He modified the rust-common.bbclass file, changing the RUSTLIB variable assignment from a hard to a soft assignment using Bitbake, which allowed for correct value overrides regardless of bbclass inheritance order. This adjustment enhanced build determinism and prevented dependency conflicts across layers. Pedro validated the propagation of RUSTLIB overrides and documented the updated variable assignment semantics, supporting future maintenance. His work demonstrated expertise in build system configuration and Bitbake, focusing on robust cross-layer compatibility within complex build environments.