fix non-git shadow builds

the qt headers live in the source dir in this configuration.

instead of hard-coding the path in the project file, use the correct
module variable. this requires harfbuzz-ng to be built after corelib.

Change-Id: If1b64b59a0939d3b5190331fcf70da566d4eeedd
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/3rdparty/harfbuzz-ng/harfbuzz-ng.pro

@@ -14,7 +14,7 @@ DEFINES += HAVE_ATEXIT
 unix: DEFINES += HAVE_PTHREAD HAVE_SCHED_H HAVE_SCHED_YIELD
 
 INCLUDEPATH += $$PWD/include
-INCLUDEPATH += $$OUT_PWD/../../../include
+INCLUDEPATH += $$QT.core.includes
 
 SOURCES += \
     $$PWD/src/hb-blob.cc \

src/src.pro

@@ -83,6 +83,7 @@ src_testlib.depends = src_corelib   # src_gui & src_widgets are not build-depend
 
 src_3rdparty_harfbuzzng.subdir = $$PWD/3rdparty/harfbuzz-ng
 src_3rdparty_harfbuzzng.target = sub-3rdparty-harfbuzzng
+src_3rdparty_harfbuzzng.depends = src_corelib   # for the Qt atomics
 
 src_angle.subdir = $$PWD/angle
 src_angle.target = sub-angle