[clang-tidy] Define __clang_analyzer__ macro for clang-tidy for compatibility...

[clang-tidy] Define __clang_analyzer__ macro for clang-tidy for compatibility with clang static analyzer

This macro is widely used in many well-known projects, ex. Chromium.
But it's not set for clang-tidy, so for ex. DCHECK in Chromium is not considered
as [[no-return]], and a lot of false-positive warnings about nullptr
dereferenced are emitted.

Differential Revision: https://reviews.llvm.org/D46325

llvm-svn: 331474