ClangToolsCompilationDb has issues with thread safety

The getCompilerOptionsBuilder function in ClangToolsCompilationDb::Private::generate(), that is passed to and run by the asynchronously run generateCompilationDB function, makes various unsafe calls into functions that are not thread safe.

ClangToolsProjectSettings::getSettings(...), and then access to that settings object; is the call to "connect" safe?; the access to diagnosticConfigs; toolExecutable(...) accesses global settings; getClangIncludeDirAndVersion(...) accesses static data unsafely