build: Use Qt top-level build facilities

depends/patches/qt/qt.pro

@@ -0,0 +1,12 @@
+# Create the super cache so modules will add themselves to it.
+cache(, super)
+
+!QTDIR_build: cache(CONFIG, add, $$list(QTDIR_build))
+
+TEMPLATE = subdirs
+SUBDIRS = qtbase qttools qttranslations
+
+qttools.depends = qtbase
+qttranslations.depends = qttools
+
+load(qt_configure)

depends/patches/qt/qttools_src.pro

@@ -0,0 +1,2 @@
+TEMPLATE = subdirs
+SUBDIRS = linguist