[llvm] [CMake] Turn on LLVM_USE_SPLIT_DWARF by default for Linux Debug build (PR #80328)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

> I'm not against trying to make the defaults better behaved for most people,

I'm very pro "better default" instead of "default to suboptimal legacy", because of discoverability, etc.
For the longest, the default cmake invocation was a Debug build, and we finally changed this to be explicit instead (that was a case where no default could be found).

ideally we'd be able to detect when the "default" aren't suitable for the current platform/toolchain and error out at CMake configuration time with a very helpful message.


https://github.com/llvm/llvm-project/pull/80328