This allows CI to screen for warnings in src and tools code. It does
not apply to examples or tests.

This is the same as commit 7012db159bc4196444ace26991b24a31e3fba495 in
qtbase.

Change-Id: I0ea00fbd4b45156dedabfd16a3cb3e5f6170f23f
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>