qt5base: remove use of QT5BASE_EXTRA_CFLAGS

This variable was added as part of an EGL i.MX6 workaround in commit
(7e9f459adf), but appears to currently be abandonded and unused.  Remove the use
of the variable.

Signed-off-by: Joshua Henderson <joshua.henderson@microchip.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/qt5/qt5base/qt5base.mk

@@ -293,8 +293,8 @@ define QT5BASE_CONFIGURE_CMDS
 		-nomake tests \
 		-device buildroot \
 		-device-option CROSS_COMPILE="$(TARGET_CROSS)" \
-		-device-option BR_COMPILER_CFLAGS="$(TARGET_CFLAGS) $(QT5BASE_EXTRA_CFLAGS)" \
-		-device-option BR_COMPILER_CXXFLAGS="$(TARGET_CXXFLAGS) $(QT5BASE_EXTRA_CFLAGS)" \
+		-device-option BR_COMPILER_CFLAGS="$(TARGET_CFLAGS)" \
+		-device-option BR_COMPILER_CXXFLAGS="$(TARGET_CXXFLAGS)" \
 		$(QT5BASE_CONFIGURE_OPTS) \
 	)
 endef