Proposed Changes

GCC 13 and newer removed implicit includes of from standard library headers. This causes the build to fail on modern compilers (like GCC 15 on Arch Linux) when compiling the vendorized CLI11 library due to uint64_t not being defined. This patch explicitly includes in externals/CLI11/CLI11.hpp to restore compatibility without breaking older compilers.

Related Work

Resolves local build failures on rolling-release Linux distributions.

System Information:

• OS: Arch Linux (Kernel 6.18.13-arch1-1)
• Compiler: GCC 15.2.1

Error Log Addressed:
../externals/CLI11/CLI11.hpp:2412:22: error: 'uint64_t' does not name a type
2412 | using result_t = uint64_t;
| ^~~~~~~~
../externals/CLI11/CLI11.hpp:152:1: note: 'uint64_t' is defined in header ''; this is probably fixable by adding '#include '

PR Checklist

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
• I used the pre-commit hook to prevent dirty commits and used pre-commit run --all to format old commits. (Note: Skipped as this is a 1-line fix to a 3rd-party vendor file)
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp), if necessary;