build-webkit should automatically set ONLY_ACTIVE_ARCH=NO when multiple architectures are specified.
As it currently stands, when we build Big Sur like this: perl ./Tools/Scripts/build-webkit --release 'ARCHS=x86_64 arm64' DEBUG_INFORMATION_FORMAT=dwarf-with-dsym CLANG_DEBUG_INFORMATION_LEVEL=line-tables-only ..we only end up with x86_64 build products because ONLY_ACTIVE_ARCH is still set to YES https://build.webkit.org/#/builders/29/builds/785/steps/7/logs/stdio
<rdar://problem/74814191>