misc/wasm: support wasmtime in wasip1

Allow switching to wasmtime through the GOWASIRUNTIME variable. This
will allow builders to run the wasip1 standard library tests against
the wasmtime WASI runtime.

For #59583

Change-Id: I4d5200df7bb27b66e041f00e89d4c2e585f5da7c
Reviewed-on: https://go-review.googlesource.com/c/go/+/485615
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Bypass: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

misc/wasm/go_wasip1_wasm_exec

@@ -3,4 +3,15 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
-exec wazero run -mount /:/ -env-inherit -cachedir "${TMPDIR}"/wazero $1 "${@:2}"
+case "$GOWASIRUNTIME" in
+	"wasmtime")
+		exec wasmtime run --dir=/ --env PWD="$PWD" --max-wasm-stack 1048576 "$1" -- "${@:2}"
+		;;
+	"wazero" | "")
+		exec wazero run -mount /:/ -env-inherit -cachedir "${TMPDIR}"/wazero "$1" "${@:2}"
+		;;
+	*)
+		echo "Unknown Go WASI runtime specified: $GOWASIRUNTIME"
+		exit 1
+		;;
+esac