Add a feature for Qt Xml

... so that we can turn it off if we don't want to build it.

Change-Id: Ia330dfa1477bcd2dc8e24eb55400e100fca156b5
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

configure.json

@@ -951,6 +951,10 @@
                 { "type": "publicQtConfig", "negative": true }
             ]
         },
+        "xml": {
+            "label": "Qt Xml",
+            "output": [ "privateFeature" ]
+        },
         "libudev": {
             "label": "udev",
             "condition": "libs.libudev",
@@ -1138,7 +1142,8 @@ Configure with '-qreal float' to create a build that is binary-compatible with 5
                 "network",
                 "sql",
                 "testlib",
-                "widgets"
+                "widgets",
+                "xml"
             ]
         }, {
             "section": "Support enabled for",

src/src.pro

@@ -124,7 +124,6 @@ src_printsupport.depends = src_corelib src_gui src_widgets src_tools_uic
 
 src_plugins.subdir = $$PWD/plugins
 src_plugins.target = sub-plugins
-src_plugins.depends = src_xml
 
 src_android.subdir = $$PWD/android
 
@@ -144,7 +143,6 @@ qtConfig(regularexpression):pcre {
 SUBDIRS += src_corelib src_tools_qlalr
 TOOLS = src_tools_moc src_tools_rcc src_tools_qlalr
 win32:SUBDIRS += src_winmain
-SUBDIRS += src_xml
 qtConfig(network) {
     SUBDIRS += src_network
     src_plugins.depends += src_network
@@ -153,6 +151,7 @@ qtConfig(sql) {
     SUBDIRS += src_sql
     src_plugins.depends += src_sql
 }
+qtConfig(xml): SUBDIRS += src_xml
 qtConfig(testlib): SUBDIRS += src_testlib
 qtConfig(dbus) {
     force_dbus_bootstrap|qtConfig(private_tests): \