Add a flag to build the documentation

The Qttools is required for the QDoc for building the docs.

Change-Id: I834d3c719b6436560b060eda70723904c5f0e6d3
Reviewed-by: Jani Heikkinen <jani.heikkinen@qt.io>
(cherry picked from commit a2160c214f)

coin/module_config.yaml

@@ -6,6 +6,9 @@ accept_configuration:
 
 instructions:
   Build:
+    - type: EnvironmentVariable
+      variableName: BUILD_DOCUMENTATION
+      variableValue: "1"
     - !include "{{qt/qtbase}}/coin_module_build_template_v2.yaml"
 
   Test:

dependencies.yaml

@@ -2,3 +2,6 @@ dependencies:
   ../qtbase:
     ref: 8fa91c75ad0cb0b1905c6775b62f734bc610fb60
     required: true
+  ../qttools:
+    ref: 7691cf0e687a3bea199061dcaf9c6dda304569af
+    required: true