Restructure building images, flashing and booting

fastboot.py

@@ -0,0 +1,36 @@
+import logging
+import subprocess
+
+
+def fastboot_erase_dtbo():
+    subprocess.run(
+        [
+            'fastboot',
+            'erase',
+            'dtbo',
+        ],
+        capture_output=True,
+    )
+
+
+def fastboot_flash(partition, file):
+    result = subprocess.run([
+        'fastboot',
+        'flash',
+        partition,
+        file,
+    ])
+    if result.returncode != 0:
+        logging.info(f'Failed to flash {file}')
+        exit(1)
+
+
+def fastboot_boot(file):
+    result = subprocess.run([
+        'fastboot',
+        'boot',
+        file,
+    ])
+    if result.returncode != 0:
+        logging.fatal(f'Failed to boot {file} using fastboot')
+        exit(1)