Set -monitor none for qemu-system-arm to enable abort via CTRL-C

Previously, you couldn't abort (the emulation step in)

```
  EXTRA_MAKEFILE=test/baremetal/platform/m55-an547/platform.mk tests func
```

via CTRL-C/SIGINT. It seems that this is related to qemu-system-arm
using CTRL-C/SIGINT for something related to the monitor console.

This commit adds `-monitor none` to the `qemu-system-arm` invocation
to disable the monitor and free up CTRL-C for interruption of the
emulation.

Signed-off-by: Hanno Becker <[email protected]>

Author: hanno-becker

test/baremetal/platform/m55-an547/exec_wrapper.py

@@ -34,7 +34,7 @@ def err(msg, **kwargs):
     fd.write(binargs)
 
 try:
-    qemu_cmd = f"qemu-system-arm -M mps3-an547 -nographic -semihosting -kernel {binpath} -device loader,file={args_file},addr=0x{cmdline_offset:x}".split()
+    qemu_cmd = f"qemu-system-arm -M mps3-an547 -monitor none -nographic -semihosting -kernel {binpath} -device loader,file={args_file},addr=0x{cmdline_offset:x}".split()
     result = subprocess.run(qemu_cmd, encoding="utf-8", capture_output=True)
 finally:
     os.unlink(args_file)