non-deterministic diagnostics (and non-deterministic PCH files). Check these when building a module rather than serializing it; it's not reasonable for a module's use to be satisfied by a definition in the user of the module. llvm-svn: 264466
llvm-svn: 264363
rare issues with nondeterministic diagnostic order, and some very common issues with nondeterministic module builds. llvm-svn: 264323