This stems from an `#include <bmalloc/BPlatform.h>` in WTF's PlatformUse.h. Many targets depend on WTF's platform headers, but they should not need to pull in bmalloc as well.
rdar://91270496
Pull request: https://github.com/WebKit/WebKit/pull/1056
Committed 254543@main (3a0b78d146f9): <https://commits.webkit.org/254543@main> Reviewed commits have been landed. Closing PR #1056 and removing active labels.