Automate generation of Chromium attribution documentation

Change-Id: I34edcc1638cdd0e0e714e247700034b517394323
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/webengine/webengine.pro

@@ -65,4 +65,22 @@ isQMLTestSupportApiEnabled() {
     DEFINES += ENABLE_SPELLCHECK
 }
 
+!build_pass {
+    chromium_attributions.commands = \
+        cd $$shell_quote($$shell_path($$PWD/../3rdparty)) && \
+        python chromium/tools/licenses.py \
+        --file-template ../../tools/about_credits.tmpl \
+        --entry-template ../../tools/about_credits_entry.tmpl credits \
+        > $$shell_quote($$shell_path($$OUT_PWD/chromium_attributions.qdoc))
+    chromium_attributions.CONFIG += phony
+
+    QMAKE_EXTRA_TARGETS += chromium_attributions
+
+    prepare_docs {
+        prepare_docs.depends += chromium_attributions
+    } else {
+        html_docs.depends += chromium_attributions
+    }
+}
+
 load(qt_module)