Clang: Watch directories instead of files

Because there a limited resources to watch files we watch now directories.
So we need much less resources.

Change-Id: Iac558832e9521a7a1a67c5ea99b42ad1b0b5129c
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/libs/utils/smallstringview.h

@@ -179,6 +179,10 @@ public:
         return m_pointer[0] == characterToSearch;
     }
 
+    char back() const { return m_pointer[m_size - 1]; }
+
+    char operator[](std::size_t index) { return m_pointer[index]; }
+
 private:
     const char *m_pointer = "";
     size_type m_size = 0;