Important
The SharePoint Framework (SPFx) used a gulp-based toolchain from SPFx v1.0 - v1.21.1. SPFx v1.22 transitioned to a new Heft-based toolchain, replacing the previous dependency on gulp. As part of this change, build toolchain configurations and customizations were also changed.
Ensure you are following the correct guidance and documentation for toolchain used by version of SPFx you're. Learn more about the different toolchains: