check(4, "RunExternalM2") failing on macos-14

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This check runs the following code:

```m2
fn=temporaryFileName()|".m2";
fn< (
startTime:=cpuTime();
while(cpuTime()-startTime"ulimit -t 2");
assert(not(r#"return code"===0));
assert(r#value===null);
```

The goal is for the `ulimit -t 2` to interrupt the function that's supposed to spin for 6 seconds after only 2 seconds. But for some reason, this isn't happening on the GitHub maos-14 runners:

```m2
-- running check(4, "RunExternalM2") -- running failed
-- error log: /var/folders/y6/nj790rtn62lfktb1sh__79hc0000gn/T/M2-35190-0/8.tmp:0:1:(3):[14]:
-- input code: /Users/runner/work/M2/M2/M2/Macaulay2/packages/RunExternalM2.m2:1051:5-1070:3
*** error: M2 exited with status code 1 -- 6.5484s elapsed
=============================================================================
/Users/runner/work/M2/M2/M2/Macaulay2/packages/RunExternalM2.m2:1051:5-1070:3 error:
-- );
-- ///<"ulimit -t 2");
-- Running (ulimit -t 2 && (/Users/runner/work/M2/M2/M2/BUILD/build/usr-dist/arm64-Darwin-macOS-14.7.6/bin/M2-binary --stop --no-debug --silent -q <"/var/folders/y6/nj790rtn62lfktb1sh__79hc0000gn/T/M2-35534-0/1.m2" >"/var/folders/y6/nj790rtn62lfktb1sh__79hc0000gn/T/M2-35534-0/1.out" 2>&1 ))
-- Finished running.
--
-- i4 : assert(not(r#"return code"===0));
-- stdio:13:6:(3): error: assertion failed
```

The failing check is in packages/RunExternalM2.m2 at lines 1051–1070. Start by running check(4, "RunExternalM2") on macos-14 and inspect how the PreRunScript ulimit -t 2 command is invoked. Done means the spinning function is interrupted, the return code is nonzero, and r#value is null.

Written by the indexing model from the issue text.