[sanitizer] Remove empty Symbolizer PrepareForSandboxing
Summary:
`Symbolizer::PrepareForSandboxing` is empty for all platforms and apparently
has been for a while (D10213). Remove it, and shuffle things around so that the
platform specific code is now in `PlatformPrepareForSandboxing`.
This allows to have one less symbolizer dependency in a common file, which
helps for the upcoming split.
Also remove `SymbolizerPrepareForSandboxing` in tsan_go which appears to not
be used anywhere.
Reviewers: alekseyshl, eugenis, dvyukov, mcgrathr
Reviewed By: alekseyshl
Subscribers: kubamracek, delcypher, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D44953
llvm-svn: 329094