qbs build: Enable the vcs module only for commercial plugins

The other ones are in the Qt Creator source tree and should not get
rebuilt on repo metadata changes, because they do not make use of
QTC_PLUGIN_REVISION.

Change-Id: I216a89de4411948b7ccad65f883d0d8782a283d4
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

qbs/imports/QtcCommercialPlugin.qbs

@@ -3,4 +3,5 @@ import qbs
 QtcPlugin {
     Depends { name: "LicenseChecker"; required: false }
     cpp.defines: base.concat(LicenseChecker.present ? ["LICENSECHECKER"] : [])
+    pluginjson.useVcsData: true
 }

qbs/imports/QtcPlugin.qbs

@@ -17,6 +17,7 @@ QtcProduct {
 
     Depends { name: "ExtensionSystem" }
     Depends { name: "pluginjson" }
+    pluginjson.useVcsData: false
     Depends {
         condition: qtc.testsEnabled
         name: "Qt.testlib"

qbs/modules/pluginjson/pluginjson.qbs

@@ -10,9 +10,10 @@ Module {
 
     // TODO: Wrap the VCS specific stuff in a dedicated module
     property bool hasVcs: Utilities.versionCompare(qbs.version, "1.10") >= 0
-    Depends { name: "vcs"; condition: hasVcs }
+    property bool useVcsData: hasVcs
+    Depends { name: "vcs"; condition: useVcsData }
     Properties {
-        condition: hasVcs
+        condition: useVcsData
         vcs.headerFileName: undefined
         vcs.repoDir: {
             // TODO: Could something like this be incorporated into the vcs module?