ClangTools: Add UI for specifying executables

Add a new group box "Executables" for this. Hide the UI for
clazy-standalone unless QTC_USE_CLAZY_STANDALONE_PATH is set as there is
no released version with the needed -export-fixes option.

Rename the previous group box from "General" to "Run Options".

Change-Id: Ia9daf66c40d3a7eea98b31d9c086886d29466490
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/coreplugin/icore.cpp

@@ -495,6 +495,11 @@ QString ICore::clangTidyExecutable(const QString &clangBinDirectory)
     return clangBinary("clang-tidy", clangBinDirectory);
 }
 
+QString ICore::clazyStandaloneExecutable(const QString &clangBinDirectory)
+{
+    return clangBinary("clazy-standalone", clangBinDirectory);
+}
+
 static QString compilerString()
 {
 #if defined(Q_CC_CLANG) // must be before GNU, because clang claims to be GNU too