Revert "Mac: INCLUDEPATH fix"

This reverts commit a7da7f8a

.

Adding the install prefix to the inlude search paths causes us to pick up
header files from there if there are any, which causes all sorts of issues.

Conflicts:
	lib/lib.pro
	shared/shared.pro

Change-Id: I070ff6443bb5612b3b7e3878d22dc9dd69d62e70
Reviewed-by: Pierre Rossi <pierre.rossi@theqtcompany.com>

src/core/core_gyp_generator.pro

@@ -29,8 +29,7 @@ else: DEFINES += QT_NO_EGL
 
 RESOURCES += devtools.qrc
 
-# something fishy with qmake in 5.2 ?
-INCLUDEPATH += $$[QT_INSTALL_HEADERS] $$PWD
+INCLUDEPATH += $$PWD
 
 SOURCES = \
         access_token_store_qt.cpp \