Mock out mgos_i2c.h to work with Linux.

src/main.c

@@ -0,0 +1,20 @@
+#include "mgos.h"
+#include "mgos_i2c.h"
+
+#define I2CBUSNR 7
+
+int main() {
+  struct mgos_i2c *i2c;
+
+  if (!mgos_i2c_open(I2CBUSNR)) {
+    LOG(LL_ERROR, ("Cannot open I2C bus %u", I2CBUSNR));
+    return -1;
+  }
+  i2c = mgos_i2c_get_global();
+  if (!i2c) {
+    LOG(LL_ERROR, ("Cannot open I2C bus"));
+    return -2;
+  }
+
+  return 0;
+}