Faster linking (-gsplit-dwarf, gold/lld, --gdb-index)

[Stephan Bergmann]

On 04/07/2018 17:37, Luboš Luňák wrote:
>   I've changed --enable-gold to --enable-ld=<linker>, because I've found out
> that LLVM besides Clang provides also a linker called lld, and lld at least
> in version 6 actually performs even better than gold (4s vs gold's 6-7s).
> There are some caveats though:
> * lld6 crashes sometimes and needs [1] (openSUSE users,
> devel:tools:compiler/libLLVM6 has it)
> * Valgrind can't handle lld's debuginfo and needs [2] and [3], or
> passing --no-rosegment to lld, see
> https://bugs.kde.org/show_bug.cgi?id=384727 (openSUSE users,
> home:llunak:my/valgrind has them)

and lld doesn't understand --dynamic-list-cpp-typeinfo, which we add for 
sanitizer (ASan/UBSan) builds in solenv/gbuild/platform/unxgcc.mk