Clang: Allow to time high-level functions

...by enabling the logging rule:

    qtc.clangbackend.timers=true

Change-Id: I085c6bbebc0343b74bcb90119d1ebb80ad49518d
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>

src/libs/clangbackendipc/clangbackendipcdebugutils.cpp

@@ -35,12 +35,15 @@
 #include <utf8string.h>
 
 #include <QDir>
+#include <QLoggingCategory>
 #include <QString>
 #include <QTemporaryDir>
 #include <QTemporaryFile>
 
 namespace {
 
+Q_LOGGING_CATEGORY(timersLog, "qtc.clangbackend.timers");
+
 class DebugInspectionDir : public QTemporaryDir
 {
 public:
@@ -96,4 +99,16 @@ Utf8String debugId(const FileContainer &fileContainer)
     return id;
 }
 
+VerboseScopeDurationTimer::VerboseScopeDurationTimer(const char *id)
+    : id(id)
+{
+    if (timersLog().isDebugEnabled())
+        timer.start();
+}
+
+VerboseScopeDurationTimer::~VerboseScopeDurationTimer()
+{
+    qCDebug(timersLog) << id << "needed" << timer.elapsed() << "ms";
+}
+
 } // namespace ClangBackEnd