fix location of injected headers in shadow builds

they are build-time generated, so they must go to the build dir
irrespective of whether we're using pre-synced headers.

Task-number: QTBUG-55585
Change-Id: I5f10b35c40b0ae2ddc5568d70e254b787ac3f914
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

mkspecs/features/qt_module_headers.prf

@@ -104,18 +104,20 @@ include($$INC_PATH/include/$$MODULE_INCNAME/headers.pri, "", true)
 
 alien_syncqt: return()
 
+MODULE_INC_OUTDIR = $$MODULE_BASE_OUTDIR/include/$$MODULE_INCNAME
+
 for (injection, SYNCQT.INJECTIONS) {
     injects = $$split(injection, :)
-    dst_hdr = $$absolute_path($$member(injects, 0), $$INC_PATH/include/$$MODULE_INCNAME)
+    dst_hdr = $$absolute_path($$member(injects, 0), $$MODULE_INC_OUTDIR)
     fwd_hdr = $$member(injects, 1)
-    MAIN_FWD = $$INC_PATH/include/$$MODULE_INCNAME/$$fwd_hdr
+    MAIN_FWD = $$MODULE_INC_OUTDIR/$$fwd_hdr
     MAIN_FWD_CONT = '$${LITERAL_HASH}include "$$relative_path($$dst_hdr, $$dirname(MAIN_FWD))"'
     write_file($$MAIN_FWD, MAIN_FWD_CONT)|error()
     touch($$MAIN_FWD, $$dst_hdr)
     !git_build: QMAKE_DISTCLEAN += $$MAIN_FWD
     injects = $$member(injects, 2, -1)
     for (inject, injects) {
-        CLASS_FWD = $$INC_PATH/include/$$MODULE_INCNAME/$$inject
+        CLASS_FWD = $$MODULE_INC_OUTDIR/$$inject
         CLASS_FWD_CONT = '$${LITERAL_HASH}include "$$fwd_hdr"'
         write_file($$CLASS_FWD, CLASS_FWD_CONT)|error()
         touch($$CLASS_FWD, $$dst_hdr)