Fix -target:js_wasm32 for core:runtime

core/runtime/default_allocators_general.odin

@@ -0,0 +1,30 @@
+//+build !windows
+//+build !freestanding
+//+build !js
+package runtime
+
+when ODIN_DEFAULT_TO_NIL_ALLOCATOR {
+	// mem.nil_allocator reimplementation
+
+	default_allocator_proc :: proc(allocator_data: rawptr, mode: Allocator_Mode,
+	                               size, alignment: int,
+	                               old_memory: rawptr, old_size: int, loc := #caller_location) -> ([]byte, Allocator_Error) {
+		return nil, .None;
+	}
+
+	default_allocator :: proc() -> Allocator {
+		return Allocator{
+			procedure = default_allocator_proc,
+			data = nil,
+		};
+	}
+} else {
+	// TODO(bill): reimplement these procedures in the os_specific stuff
+	import "core:os"
+
+	default_allocator_proc :: os.heap_allocator_proc;
+
+	default_allocator :: proc() -> Allocator {
+		return os.heap_allocator();
+	}
+}