Attempt `edgetpu-compiler` autoinstall (#6223)

* Attempt `edgetpu-compiler` autoinstall

Attempt to install edgetpu-compiler dependency if missing on Linux.

* Update export.py

* Update export.py

export.py

@@ -309,11 +309,16 @@ def export_edgetpu(keras_model, im, file, prefix=colorstr('Edge TPU:')):
     # YOLOv5 Edge TPU export https://coral.ai/docs/edgetpu/models-intro/
     try:
         cmd = 'edgetpu_compiler --version'
-        help = 'See https://coral.ai/docs/edgetpu/compiler/'
-        assert platform.system() == 'Linux', f'export only supported on Linux. {help}'
-        assert subprocess.run(cmd, shell=True).returncode == 0, f'export requires edgetpu-compiler. {help}'
-        out = subprocess.run(cmd, shell=True, capture_output=True, check=True)
-        ver = out.stdout.decode().split()[-1]
+        help_url = 'https://coral.ai/docs/edgetpu/compiler/'
+        assert platform.system() == 'Linux', f'export only supported on Linux. See {help_url}'
+        if subprocess.run(cmd, shell=True).returncode != 0:
+            LOGGER.info(f'\n{prefix} export requires Edge TPU compiler. Attempting install from {help_url}')
+            for c in ['curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -',
+                      'echo "deb https://packages.cloud.google.com/apt coral-edgetpu-stable main" | sudo tee /etc/apt/sources.list.d/coral-edgetpu.list',
+                      'sudo apt-get update',
+                      'sudo apt-get install edgetpu-compiler']:
+                subprocess.run(c, shell=True, check=True)
+        ver = subprocess.run(cmd, shell=True, capture_output=True, check=True).stdout.decode().split()[-1]
 
         LOGGER.info(f'\n{prefix} starting export with Edge TPU compiler {ver}...')
         f = str(file).replace('.pt', '-int8_edgetpu.tflite')  # Edge TPU model