[clang] [llvm] [Clang] Emit DW_TAG_template_alias for template aliases (PR #87623)

[David Blaikie via cfe-commits]

dwblaikie wrote:

> > I'm a little uncomfortable with adding a new user-facing option for template aliases. Even with that in place, we should not warn and refuse to do what the user asked for, based on DWARF version. -gdwarf-2 -gsplit-dwarf generates a .dwo file claiming to be v2, for example.
> 
> I don't have strong feelings about the flag setup and am happy to change it. @dwblaikie mentioned that we might not want to have the debugger tuning be the only way of controlling whether or not we emit this DIE, so adding `-gtemplate-alias` which has its default set based on debugger tuning seemed like a reasonable way of doing it. What would be the best way of controlling this feature in your opinion (bearing in mind that GCC doesn't emit it, and GDB and LLDB don't the DIE)?

@pogo59 Hmm - I thought you held a strong preference that debugger tuning never be the only way to access a certain feature, and that we should always have direct control of these features via flags (but with default (or explicit) debugger tuning setting some of these flag defaults based on the preferred content for that debugger). Perhaps i'm misremembering?

https://github.com/llvm/llvm-project/pull/87623