runtime, targets: some WIP on wasm unknown in part from PR #3072

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/runtime/runtime_wasm_unknown.go

@@ -0,0 +1,49 @@
+//go:build wasm_unknown
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+type timeUnit int64
+
+// libc constructors
+//
+//export __wasm_call_ctors
+func __wasm_call_ctors()
+
+//export _start
+func _start() {
+	// These need to be initialized early so that the heap can be initialized.
+	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
+	heapEnd = uintptr(wasm_memory_size(0) * wasmPageSize)
+	run()
+}
+
+// Read the command line arguments from WASI.
+// For example, they can be passed to a program with wasmtime like this:
+//
+//	wasmtime run ./program.wasm arg1 arg2
+func init() {
+	__wasm_call_ctors()
+}
+
+var args []string
+
+func ticksToNanoseconds(ticks timeUnit) int64 {
+	return int64(ticks)
+}
+
+func nanosecondsToTicks(ns int64) timeUnit {
+	return timeUnit(ns)
+}
+
+const timePrecisionNanoseconds = 1000 // TODO: how can we determine the appropriate `precision`?
+
+func sleepTicks(d timeUnit) {
+}
+
+func ticks() timeUnit {
+	return timeUnit(0)
+}