all: basic support for the os package

The resulting binary is pretty big due to lacking optimizations
(probably because of interfaces), so that should be fixed.

src/runtime/atomic.go

@@ -0,0 +1,24 @@
+package runtime
+
+// This file contains implementations for the sync/atomic package.
+
+// All implementations assume there are no goroutines, threads or interrupts.
+
+//go:linkname loadUint64 sync/atomic.LoadUint64
+func loadUint64(addr *uint64) uint64 {
+	return *addr
+}
+
+//go:linkname storeUint32 sync/atomic.StoreUint32
+func storeUint32(addr *uint32, val uint32) {
+	*addr = val
+}
+
+//go:linkname compareAndSwapUint64 sync/atomic.CompareAndSwapUint64
+func compareAndSwapUint64(addr *uint64, old, new uint64) bool {
+	if *addr == old {
+		*addr = new
+		return true
+	}
+	return false
+}