configure: reload spec after configuring paths

this fixes the x-build for raspberry pi, as that spec refers to the
sysroot.

the path setup doesn't require the device options to be in effect yet,
so it was sufficient to move the existing spec reload to a later point
in time.

Change-Id: Idc521aa13ff441931e954c7c9004472cf7061ee1
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

configure.json

@@ -423,7 +423,7 @@
 
     "features": {
         "prepare": {
-            "output": [ "prepareSpec", "prepareOptions", "preparePaths" ]
+            "output": [ "prepareSpec", "prepareOptions", "preparePaths", "reloadSpec" ]
         },
         "machineTuple": {
             "condition": "!config.linux || config.android || tests.machineTuple",

configure.pri

@@ -593,9 +593,8 @@ defineTest(qtConfOutput_prepareOptions) {
 
     export($${currentConfig}.output.devicePro)
 
-    # reload the spec to make the settings actually take effect.
-    !isEmpty($${currentConfig}.output.devicePro): \
-        reloadSpec()
+    # if any settings were made, the spec will be reloaded later
+    # to make them take effect.
 }
 
 defineTest(qtConfOutput_machineTuple) {
@@ -842,6 +841,15 @@ defineTest(qtConfOutput_preparePaths) {
             "Prefix=$$QT_SOURCE_TREE"
     write_file($$QT_BUILD_TREE/bin/qt.conf, cont)|error()
     reload_properties()
+
+    # if a sysroot was configured, the spec will be reloaded later,
+    # as some specs contain $$[SYSROOT] references.
+}
+
+defineTest(qtConfOutput_reloadSpec) {
+    !isEmpty($${currentConfig}.output.devicePro)| \
+            !isEmpty(config.input.sysroot): \
+        reloadSpec()
 }
 
 defineTest(qtConfOutput_shared) {