fixes#25735
This pull request updates how string-to-C-string conversions are handled
when the `nimsso` configuration flag is enabled, and adds a new system
test to validate the behavior. The main changes focus on switching from
using `addrLoc` to `byRefLoc` for argument preparation, which likely
improves correctness or compatibility with the `nimsso` mode.
**Code generation improvements for `nimsso` mode:**
* In both `compiler/ccgcalls.nim` (`genArgStringToCString`) and
`compiler/ccgexprs.nim` (`convStrToCStr`), replaced the use of `addrLoc`
with `byRefLoc` when preparing arguments for string-to-C-string
conversions under the `nimsso` configuration flag. This change ensures
that references are handled appropriately according to the requirements
of `nimsso`.
[[1]](diffhunk://#diff-42181cc6f4202af843e7835ea514df2efe85e4faae3bc797a39a0c422547b558L373-R373)
[[2]](diffhunk://#diff-4509107d295d7d32b1887c8993cd0f56113ae60f36113e7d8778646dabd92ebcL2739-R2739)
**Testing:**
* Added a new system test `tests/system/tnimsso.nim` that runs with the
`-d:nimsso` flag on both C and C++ targets, checking that
string-to-C-string conversion works as expected in `nimsso` mode.
7b73537131