[R] mclapply hanging occasionally on macos

[Ivo Welch]

sequoia, 15.2.  R --vanilla : 4.4.2 (2024-10-31).  I have the same
basic setup on three macs: a macbook air, a mac pro m1, and a mac mini
m4.  The following code is running into a bug on the mac pro m1 and
the mac mini, but works just fine on my macbook air.  (of course, it
doesn't do anything useful.)  it's replicable!

```
$ R --vanilla
> source("debug.R")
```

and (after putting a single word into debug.csv in order to avoid the
empty file error),

```
library(parallel)

ignore.dataset <- read.csv("debug.csv"); rm(ignore.dataset)

useless.function <- function( ) {
    y <- rnorm(3); x <- rnorm(3)
    summary( lm( y ~ x ))  ## useless
    NULL
}

run30 <- function(i) {
    message("run30=", i)
    useless.function()
}

run30( 0 )
message("many mc")
simsl <- mclapply( 1:30, run30 )
```

this replicably does not count to 30 on both desktops, but does on the air.

not fun...can someone else try this program on a macos recent desktop,
and let me know whether I am alone here?

/iaw