signal errors in ci_fetch_deps subprocesses

A recent build failed. The original error seemed to be during ci_fetch_deps
where a build message said
```
  fatal: reference is not a tree: 346c936e14c6ea3a8d3d65cb1fa46202dc92999d
  fatal: Unable to checkout '346c936e14c6ea3a8d3d65cb1fa46202dc92999d' in submodule path 'extmod/ulab'
```
(along with other problems), but this step didn't signal failure to
github actions.

By adding the check= parameter, a failure of the subprocess will cause
a CalledProcessError to be raised, which will make ci_fetch_deps exit with
nonzero status. In turn, this should let Actions understand that something
went wrong with this step, instead of waiting for some subsequent step(s)
to go wrong.

Author: jepler

tools/ci_fetch_deps.py

@@ -47,9 +47,11 @@ def run(title, command):
     print("::group::" + title, flush=True)
     print(command, flush=True)
     start = time.monotonic()
-    subprocess.run(shlex.split(command), stderr=subprocess.STDOUT)
-    print("Duration:", time.monotonic() - start, flush=True)
-    print("::endgroup::", flush=True)
+    try:
+        subprocess.run(shlex.split(command), stderr=subprocess.STDOUT, check=True)
+    finally:
+        print("Duration:", time.monotonic() - start, flush=True)
+        print("::endgroup::", flush=True)
 
 
 run(