Add a means to handle dynamically created qmldir files

This will enable modules like QtWebView which needs to generate its
qmldir at qmake time since it changes depending on whether QtWebEngine
is available or not. This ensures that it is not created in the sources
directory and in the build directory and correctly picked up.

Task-number: QTBUG-65092
Change-Id: Iac628b97145d29778f554510e8e07102d588df64
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

mkspecs/features/qml_module.prf

@@ -13,7 +13,14 @@ equals(TEMPLATE, app): TEMPLATE = aux
 
 isEmpty(TARGETPATH): error("Must set TARGETPATH (QML import name)")
 
-qmldir_file = $$_PRO_FILE_PWD_/qmldir
+!isEmpty(DYNAMIC_QMLDIR) {
+    qmldir_path = $$OUT_PWD
+    write_file($${qmldir_path}/qmldir, DYNAMIC_QMLDIR)|error("Aborting.")
+} else {
+    qmldir_path = $$_PRO_FILE_PWD_
+}
+
+qmldir_file = $${qmldir_path}/qmldir
 
 fq_qml_files =
 for(qmlf, QML_FILES): fq_qml_files += $$absolute_path($$qmlf, $$_PRO_FILE_PWD_)
@@ -42,13 +49,20 @@ builtin_resources {
 }
 
 # Install rules
-qmldir.base = $$_PRO_FILE_PWD_
+qmldir.base = $$qmldir_path
 # Tools need qmldir and plugins.qmltypes always installed on the file system
-qmldir.files = $$qmldir_file $$fq_aux_qml_files
+
+qmldir.files = $$qmldir_file
 install_qml_files: qmldir.files += $$fq_qml_files
 qmldir.path = $$[QT_INSTALL_QML]/$$TARGETPATH
 INSTALLS += qmldir
 
+qmlfiles.base = $$_PRO_FILE_PWD_
+qmlfiles.files = $$fq_aux_qml_files
+install_qml_files: qmlfiles.files += $$fq_qml_files
+qmlfiles.path = $${qmldir.path}
+INSTALLS += qmlfiles
+
 !debug_and_release|!build_all|CONFIG(release, debug|release) {
     !prefix_build {
         COPIES += qmldir