wasm: add support for GOOS=wasip1

This adds true GOOS=wasip1 support in addition to our existing
-target=wasi support. The old support for WASI isn't removed, but should
be treated as deprecated and will likely be removed eventually to reduce
the test burden.

src/runtime/env.go

@@ -1,4 +1,4 @@
-//go:build linux || darwin || windows
+//go:build linux || darwin || windows || wasip1
 
 package runtime
 

src/runtime/env_unix.go

@@ -1,4 +1,4 @@
-//go:build linux || darwin
+//go:build linux || darwin || wasip1
 
 package runtime
 

src/runtime/os_wasip1.go

@@ -0,0 +1,10 @@
+//go:build wasip1
+
+package runtime
+
+// The actual GOOS=wasip1, as newly added in the Go 1.21 toolchain.
+// Previously we supported -target=wasi, but that was essentially faked by using
+// linux/arm instead because that was the closest thing that was already
+// supported in the Go standard library.
+
+const GOOS = "wasip1"

src/runtime/runtime_wasm_js.go

@@ -1,4 +1,4 @@
-//go:build wasm && !wasi
+//go:build wasm && !wasi && !wasip1
 
 package runtime
 

src/runtime/runtime_wasm_js_scheduler.go

@@ -1,4 +1,4 @@
-//go:build wasm && !wasi && !scheduler.none
+//go:build wasm && !wasi && !scheduler.none && !wasip1
 
 package runtime
 

src/runtime/runtime_wasm_wasi.go

@@ -1,4 +1,4 @@
-//go:build tinygo.wasm && wasi
+//go:build tinygo.wasm && (wasi || wasip1)
 
 package runtime