Fix another build issue.

Change-Id: Ie9e9f707bb2e89f40064415289aa44770c028ae7
Reviewed-by: Joerg Bornemann <joerg.bornemann@nokia.com>

src/plugins/vcsbase/vcsbase.qbs

@@ -12,6 +12,7 @@ QtcPlugin {
     Depends { name: "cpp" }
     Depends { name: "qt"; submodules: ['gui'] }
     Depends { name: "CppTools" }
+    Depends { name: "CPlusPlus" }
 
     cpp.includePaths: [
         ".",