[Chapel Merge] Fix a c_string to string assignment in the Spawn m

Branch: refs/heads/master
Revision: 2955609
Author: e-kayrakli
Log Message:

Merge pull request #16799 from e-kayrakli/fix-spawn-cstr-depr

Fix a c_string to string assignment in the Spawn module

https://github.com/chapel-lang/chapel/pull/16792 deprecated assigning from a
c_string to Chapel string. However, there’s one usage of that left in the Spawn
module that’s executed only on ugni. This PR changes that use to use
createStringWithNewBuffer instead.

[Trivial, not reviewed]

Test:

  • [x] test/library/standard/Spawn/ugni compiles without warning.

Modified Files:
M modules/standard/Spawn.chpl

Compare: https://github.com/chapel-lang/chapel/compare/43d3956a1e99...2955609d60f8