fix(FTBFS): meson: raise C++ standard to C++17
LLVM 16 requires this since LLVM commit b4e9977fc18 and instead of just going all over the various directories and adding overrides it should be easier to just raise this globally. GCC supports C++17 since GCC 8 (2018), Clang since version 5 (2017). Debian Buster (oldstable) has GCC 8.3 and Clang 7.0, so all major distributions should have this and there shouldn't be an issue with bumping.
- Closes: #7031 (closed), #7081 (closed)
- Signed-off-by: Kai Wasserbäch kai@dev.carbon-project.org
- Reviewed-by: Jesse Natalie jenatali@microsoft.com
- Reviewed-by: David Heidelberg david.heidelberg@collabora.com