[m-rev.] for post-commit review: write_string_to_a_file

[Zoltan Somogyi]

For review by anyone. The code changes are mostly straightforward;
the part I am seeking feedback on is whether anyone knows for sure
whether two different mmake actions can update the same .d file
at the "same" time.

Zoltan.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Log.wstf
Type: application/octet-stream
Size: 834 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20240802/f860f0e5/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: DIFF.wstf
Type: application/octet-stream
Size: 18536 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20240802/f860f0e5/attachment-0003.obj>