qbs build: Prefer KSyntaxHighlighting from system

Note that the system package will only be found with qbs >= 1.20.

Change-Id: I361b774d6b35fdbd0386144d4e9812f02f7841e5
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

qbs/modules/qtc/qtc.qbs

@@ -68,6 +68,8 @@ Module {
     property bool enableUbSanitizer: false
     property bool enableThreadSanitizer: false
 
+    property bool preferSystemSyntaxHighlighting: true
+
     property bool make_dev_package: false
 
     // Will be replaced when creating modules from products

src/libs/3rdparty/syntax-highlighting/syntax-highlighting.qbs

@@ -4,9 +4,27 @@ import qbs.FileInfo
 import qbs.Environment
 
 Project {
-    QtcLibrary {
+    Product {
         name: "KSyntaxHighlighting"
 
+        Export {
+            Depends { name: "qtc" }
+            Depends {
+                name: "Qt.KSyntaxHighlighting"
+                condition: qtc.preferSystemSyntaxHighlighting
+                required: false
+            }
+            Depends {
+                name: "KSyntaxHighlighting_bundled"
+                required: !qtc.preferSystemSyntaxHighlighting
+            }
+        }
+    }
+
+    QtcLibrary {
+        name: "KSyntaxHighlighting_bundled"
+        condition: !qtc.preferSystemSyntaxHighlighting || !Qt.KSyntaxHighlighting.present
+
         cpp.defines: base.concat("KSYNTAXHIGHLIGHTING_LIBRARY")
         cpp.includePaths: [
             product.sourceDirectory + "/src/lib/",
@@ -16,6 +34,11 @@ Project {
 
         Depends { name: "Qt.gui" }
         Depends { name: "Qt.network" }
+        Depends {
+            name: "Qt.KSyntaxHighlighting"
+            condition: qtc.preferSystemSyntaxHighlighting
+            required: false
+        }
 
         Group {
             name: "lib"