CppTools: Turn some classes into pure value types

ProjectInfo, ProjectPart and ProjectUpdateInfo used to carry pointers
to Project and/or Toolchain, even though they were used in contexts
where these pointers were either unsafe to access or not guaranteed to
be valid anymore, which made their use difficult and error-prone.
We turn these classes into pure value types by copying in all relevant
information before the first async operation takes place.

Fixes: QTCREATORBUG-25678
Change-Id: I1914b0dbda6c7dfba6c95e5e92f2d69977755590
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/cpptools/compileroptionsbuilder.cpp

@@ -666,8 +666,8 @@ void CompilerOptionsBuilder::addIncludeDirOptionForPath(const ProjectExplorer::H
             systemPath = true;
     } else {
         // ProjectExplorer::HeaderPathType::User
-        if (m_useSystemHeader == UseSystemHeader::Yes
-            && !path.path.startsWith(m_projectPart.project->rootProjectDirectory().toString())) {
+        if (m_useSystemHeader == UseSystemHeader::Yes && m_projectPart.hasProject()
+            && !Utils::FilePath::fromString(path.path).isChildOf(m_projectPart.topLevelProject)) {
             systemPath = true;
         }
     }