[gn build] Add build files for clang/lib/{ASTMatchers,CrossTU},...

[gn build] Add build files for clang/lib/{ASTMatchers,CrossTU}, clang/lib/StaticAnalyzer/{Checkers,Core,Frontend}

The intent is to add the build file for clang/lib/StaticAnalyzer/Frontend; everything else is pulled in by that.

Differential Revision: https://reviews.llvm.org/D55978

llvm-svn: 349986