add fallback stub for aarch64

Author: leongross

src/os/exec_linux_aarch64.go

@@ -0,0 +1,15 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux && !baremetal && !tinygo.wasm && aarch64
+
+package os
+
+import "errors"
+
+// On the aarch64 architecture, the fork system call is not available.
+// Therefore, the fork function is implemented to return an error.
+func startProcess(name string, argv []string, attr *ProcAttr) (p *Process, err error) {
+	return nil, errors.New("fork not yet supported on aarch64")
+}

src/os/osexec.go

@@ -1,4 +1,4 @@
-//go:build linux && !baremetal && !darwin && !tinygo.wasm && !arm64
+//go:build linux && !baremetal && !darwin && !tinygo.wasm && !aarch64
 
 // arm64 does not have a fork syscall, so ignore it for now
 // TODO: add support for arm64 with clone or use musl implementation