fbt: exclude user site-packages directory from sys.path (#1778)

* fbt: exclude user site-packages directory from sys.path
* fbt: python path fixes for *nix
* fbt: fixed cli target on Windows

Co-authored-by: hedger <hedger@users.noreply.github.com>

scripts/serial_cli.py

@@ -1,13 +1,25 @@
 import logging
 import subprocess
 from flipper.utils.cdc import resolve_port
+import os
+import sys
 
 
 def main():
     logger = logging.getLogger()
     if not (port := resolve_port(logger, "auto")):
+        logger.error("Is Flipper connected over USB and isn't in DFU mode?")
         return 1
-    subprocess.call(["python3", "-m", "serial.tools.miniterm", "--raw", port, "230400"])
+    subprocess.call(
+        [
+            os.path.basename(sys.executable),
+            "-m",
+            "serial.tools.miniterm",
+            "--raw",
+            port,
+            "230400",
+        ]
+    )
 
 
 if __name__ == "__main__":