[Sanitizers] Basic Solaris sanitizer support (PR 33274)

Summary:
This patch (on top of https://reviews.llvm.org/D35755) provides the clang side necessary
to enable the Solaris port of the sanitizers implemented by https://reviews.llvm.org/D40898,
https://reviews.llvm.org/D40899, and https://reviews.llvm.org/D40900).

A few features of note:

* While compiler-rt cmake/base-config-ix.cmake (COMPILER_RT_OS_DIR) places
  the runtime libs in a tolower(CMAKE_SYSTEM_NAME) directory, clang defaults to
  the OS part of the target triplet (solaris2.11 in the case at hand).  The patch makes
  them agree on compiler-rt's idea.

* While Solaris ld accepts a considerable number of GNU ld options for compatibility,
  it only does so for the double-dash forms.  clang unfortunately is inconsistent here
  and sometimes uses the double-dash form, sometimes the single-dash one that
  confuses the hell out of Solaris ld.  I've changed the affected places to use the double-dash
  form that should always work.

* As described in https://reviews.llvm.org/D40899, Solaris ld doesn't create the
  __start___sancov_guards/__stop___sancov_guards labels gld/gold/lld do, so I'm
  including additional runtime libs into the link that provide them.

* One test uses -fstack-protector, but unlike other systems libssp hasn't been folded
  into Solaris libc, but needs to be linked with separately.

* For now, only 32-bit x86 asan is enabled on Solaris.  64-bit x86 should follow, but
  sparc (which requires additional compiler-rt changes not yet submitted) fails miserably
  due to a llvmsparc backend limitation:

fatal error: error in backend: Function "_ZN7testing8internal16BoolFromGTestEnvEPKcb": over-aligned dynamic alloca not supported.

  However, inside the gcc tree, Solaris/sparc asan works almost as well as x86.

Reviewers: rsmith, alekseyshl

Reviewed By: alekseyshl

Subscribers: jyknight, fedor.sergeev, cfe-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D40903

llvm-svn: 324296