Allow Qt for UIKit to be built as shared libraries and default to it

Instead of forcing a static build, configure now respects the
-shared flag and defaults to that.

[ChangeLog][Important Behavior Changes] Qt for iOS now respects the
-shared configure flag, and now defaults to this configuration as with
all other platforms.

Task-number: QTBUG-42937
Change-Id: I9e7b2de8f7f8ba031c2610ff5ac0858e357424bd
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

configure.json

@@ -462,7 +462,7 @@
     "features": {
         "shared": {
             "label": "Building shared libraries",
-            "condition": "!config.uikit && !config.integrity",
+            "condition": "!config.integrity",
             "output": [
                 "shared",
                 "publicFeature",

mkspecs/features/uikit/default_pre.prf

@@ -20,3 +20,6 @@ load(default_pre)
 # Check for supported Xcode versions
 lessThan(QMAKE_XCODE_VERSION, "4.3"): \
     error("This mkspec requires Xcode 4.3 or later")
+
+ios:shared:lessThan(QMAKE_IOS_DEPLOYMENT_TARGET, "8.0"): \
+    QMAKE_IOS_DEPLOYMENT_TARGET = 8.0

src/plugins/platforms/ios/ios.pro

@@ -1,5 +1,10 @@
 TARGET = qios
 
+# QTBUG-42937: Work around linker errors caused by circular
+# dependencies between the iOS platform plugin and the user
+# application's main() when the plugin is a shared library.
+qtConfig(shared): CONFIG += static
+
 QT += core-private gui-private platformsupport-private
 LIBS += -framework Foundation -framework UIKit -framework QuartzCore -framework AudioToolbox