configure: fix detection of xcb extensions

- Properly detect xcb-render and xkb features.
  a) when -qt-xcb, use bundled versions
  b) when -system-xcb, detect from system

- Be consistent with other features (jpeg, png)
  in "enable"/"disable" field handling.

- And move the "xkb" feature higer up in configure.json.
  It is an X11 extension, so keep them all together (instead
  of grouping it with libxkbcommon).

Task-number: QTBUG-59064
Change-Id: I60f95fb37060b8abde4c611cdef178ba3795982c
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

src/gui/configure.json

@@ -224,7 +224,7 @@
             ]
         },
         "xcb_syslibs": {
-            "label": "XCB (secondary)",
+            "label": "XCB (extensions)",
             "test": "qpa/xcb-syslibs",
             "sources": [
                 { "type": "pkgConfig",
@@ -701,11 +701,11 @@
             "output": [ "privateFeature" ]
         },
         "system-xcb": {
-            "label": "Using system provided XCB libraries",
-            "enable": "input.xcb == 'system' || input.xcb == 'yes'",
-            "disable": "input.xcb == 'qt' || input.xcb == 'no'",
+            "label": "Using system-provided XCB libraries",
+            "enable": "input.xcb == 'system'",
+            "disable": "input.xcb == 'qt'",
             "autoDetect": "!config.darwin",
-            "condition": "libs.xcb && libs.xcb_syslibs",
+            "condition": "features.xcb && libs.xcb_syslibs",
             "output": [ "privateFeature" ]
         },
         "x11-prefix": {
@@ -721,8 +721,14 @@
         },
         "xcb-render": {
             "label": "XCB render",
-            "emitIf": "features.system-xcb",
-            "condition": "libs.xcb_render",
+            "emitIf": "features.xcb",
+            "condition": "!features.system-xcb || libs.xcb_render",
+            "output": [ "privateFeature" ]
+        },
+        "xkb": {
+            "label": "XCB XKB",
+            "emitIf": "features.xcb",
+            "condition": "!features.system-xcb || libs.xcb_xkb",
             "output": [ "privateFeature" ]
         },
         "xcb-xlib": {
@@ -739,6 +745,7 @@
         },
         "xinput2": {
             "label": "Xinput2",
+            "emitIf": "features.xcb",
             "condition": "libs.xinput2",
             "output": [ "privateFeature" ]
         },
@@ -755,11 +762,6 @@
             "condition": "libs.xkbcommon_x11",
             "output": [ "privateFeature" ]
         },
-        "xkb": {
-            "label": "XCB XKB",
-            "condition": "features.system-xcb && libs.xcb_xkb",
-            "output": [ "privateFeature" ]
-        },
         "xkb-config-root": {
             "label": "XKB config root",
             "emitIf": "features.xcb",