build: clean up the mess of ifdefs from platform into a scons-configured hal

src/Hal.h

@@ -0,0 +1,30 @@
+#pragma once
+
+struct BootOptions;
+
+typedef enum {
+  HAL_UNKNOWN,
+  HAL_ESP32,
+  HAL_ESP8266
+} HalBackend;
+
+constexpr HalBackend DefaultBackend = HAL_ESP8266;
+
+template<HalBackend Backend = DefaultBackend>
+class PlatformImpl {
+  public:
+    static const char* name();
+    static const char* version();
+    static int freeRam();
+    static void startWatchdog();
+    static void startNTP();
+    static bool getLocalTime(struct tm* timedata, int timezone);
+    static void loop();
+    static const char* deviceID();
+    __attribute__((noreturn)) static void restart();
+    static void bootSplash();
+    static void printCrashInfo();
+
+    static void initBootOptions(BootOptions& opts);
+    static void forceSafeMode();
+};