This is enough to get tbb to build and test successfully on aarch64.
Index: patches/patch-build_OpenBSD_inc =================================================================== RCS file: patches/patch-build_OpenBSD_inc diff -N patches/patch-build_OpenBSD_inc --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ patches/patch-build_OpenBSD_inc 29 Dec 2018 18:18:06 -0000 @@ -0,0 +1,15 @@ +$OpenBSD$ + +Index: build/OpenBSD.inc +--- build/OpenBSD.inc.orig ++++ build/OpenBSD.inc +@@ -24,6 +24,9 @@ ifndef arch + ifeq ($(shell uname -m),amd64) + export arch:=intel64 + endif ++ ifeq ($(shell uname -m),arm64) ++ export arch:=aarch64 ++ endif + endif + + ifndef runtime
