Index: contrib/elftoolchain/common/native-elf-format
===================================================================
--- contrib/elftoolchain/common/native-elf-format
+++ contrib/elftoolchain/common/native-elf-format
@@ -39,6 +39,8 @@
             elfarch = "EM_X86_64";
         } else if (match($0, "PowerPC64")) {
             elfarch = "EM_PPC64";
+        } else if (match($0, "AArch64")) {
+            elfarch = "EM_AARCH64";
         } else {
             elfarch = "unknown";
         }
Index: tools/build/Makefile
===================================================================
--- tools/build/Makefile
+++ tools/build/Makefile
@@ -125,6 +125,9 @@
 .if ${_host_arch} == "x86_64"
 # bmake on Linux/mac often prints that instead of amd64
 _host_arch=amd64
+.elif ${_host_arch} == "aarch64"
+# Linux calls arm64, aarch64, across the board
+_host_arch=arm64
 .elif ${_host_arch:Mppc*}
 _host_arch=powerpc
 .endif