Fix that clang static analyzer did not find built-in headers

Clang expects these to lie in "../lib/clang" relative to the clang
executable.

Change-Id: I216860876591dca1fd728e4b1e79b4b07c965620
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/clangstaticanalyzer/clangstaticanalyzersettings.cpp

@@ -60,8 +60,9 @@ static QString clangExecutableFileName()
 
 QString ClangStaticAnalyzerSettings::defaultClangExecutable() const
 {
-    const QString shippedBinary = Core::ICore::libexecPath() + QLatin1Char('/')
-            + clangExecutableFileName();
+    const QString shippedBinary = Core::ICore::libexecPath()
+                    + QLatin1String("/clang/bin/")
+                    + clangExecutableFileName();
     if (QFileInfo(shippedBinary).isExecutable())
         return shippedBinary;
     return clangExecutableFileName();