CMake: SwiftCore: Add back SWIFT_STDLIB_SUPPORTS_BACKTRACE_REPORTING

[etcwilde]

So, despite the name, this is not the same as enabling backtracing.... Somehow. Anyway, this was a macro from the old build that we want in the new build.

@mikeash and @al45tair, is there some way that we can merge these concepts or at least have a better description of how they differ.

rdar://142440689

[compnerd]

This is not confusing at all 🤦‍♂️

[al45tair]

This setting controls the backtrace that you get from fatalError(), which ends up calling reportNow() in Errors.cpp; there are a few other things that use this path also, mostly where the runtime is directly emitting diagnostics. Having the backtracer take over these backtraces is on my list of things to do (rdar://113562509).

[etcwilde]

This setting controls the backtrace that you get from fatalError(), which ends up calling reportNow() in Errors.cpp; there are a few other things that use this path also, mostly where the runtime is directly emitting diagnostics.

Okay, I can give this a better description then.

[etcwilde]

@swift-ci please smoke test

[etcwilde]

@swift-ci please smoke test Windows

[etcwilde]

@swift-ci please smoke test

[etcwilde]

@swift-ci please test Windows

[etcwilde]

@swift-ci please smoke test

[xavgru12]

Do we not have a formatter that formats the CMakeLists to a defined style?

[etcwilde]

Do we not have a formatter that formats the CMakeLists to a defined style?

No. I am trying to keep it at least somewhat consistent within the new parts of the build with two-space indentation and putting closing parens on the last line, but that's about it.