Retain sccsid symbol in native libs - #6830

We started using --gc-sections linker flag (aggressing trimming of binaries) in dotnet/runtime#128232 and @tmds caught it in time.

ok makes sense. there's another one in https://github.com/dotnet/runtime/blob/4e4d02afbe0b8144c8b3c8f1fdf25cacf5663b3c/src/coreclr/inc/corhlprpriv.h#L185-L188 and https://github.com/dotnet/diagnostics/blob/edf66fc88f26651024498cb7443eded5fa805439/src/shared/inc/corhlprpriv.h#L185-L189, not sure if they should be fixed in the same PR

Those are probably not even needed, lets see: dotnet/diagnostics#5856 😅

Those are probably not even needed, lets see: dotnet/diagnostics#5856

The build of some legs fails due to the removal of the used attribute

Those are probably not even needed, lets see: dotnet/diagnostics#5856

The build of some legs fails due to the removal of the used attribute

@janvorli, interestingly, dotnet/runtime#128575 is only reported for shared libs from src/native/libs, coreclr libs are retaining sccsid even without this fix (although copilot's PR dotnet/runtime#128232 unconditionally applied the change). I haven't figured out why --gc-sections is less diligent in coreclr subset; sounds like it's leaving some stuff on the table (or perhaps linker has different dead code analyzer for C vs. C++)? My premise of last commit based on @akoeplinger's comment was if it didn't failed in corhlprpriv.h without retain attribute, then used isn't needed; but after a careful look, it's actually difference in compiler toolchain analysis of dead code.