Use a custom platformio py file to always set build version

bin/platformio-custom.py

@@ -0,0 +1,17 @@
+import configparser
+
+config = configparser.RawConfigParser()
+config.read('version.properties')
+
+version = dict(config.items('VERSION'))
+
+verStr = "{}.{}.{}".format(version["major"], version["minor"], version["build"])
+
+print(f"Using meshtastic platform-custom.py, firmare version {verStr}")
+
+Import("env", "projenv")
+
+# General options that are passed to the C and C++ compilers
+projenv.Append(CCFLAGS=[
+    f"-DAPP_VERSION={verStr}"
+    ])