[Bug sanitizer/88022] Support dynamic shadow offset in ASan

[chefmax at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88022

--- Comment #2 from chefmax at gcc dot gnu.org ---
I think nothing prevents us from trying several ranges, the question is whether
upstream guys will accept this...
I've just noticed that the code for dynamic shadow offset is already present in
libsanitizer sources and it seems that it's not hard to enable it for Linux.