qt5base: use ccache if enabled

For now, it doesn't use ccache when compiling host tools (e.g. qmake).
It seems the fix is not trivial.

Signed-off-by: Fatih Aşıcı <fatih.asici@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qt5/qt5base/qt5base.mk

@@ -167,7 +167,7 @@ define QT5BASE_CONFIGURE_CMDS
 		-no-rpath \
 		-nomake examples -nomake tests \
 		-device buildroot \
-		-device-option CROSS_COMPILE="$(TARGET_CROSS)" \
+		-device-option CROSS_COMPILE="$(CCACHE) $(TARGET_CROSS)" \
 		-device-option BUILDROOT_COMPILER_CFLAGS="$(TARGET_CFLAGS)" \
 		-device-option BUILDROOT_COMPILER_CXXFLAGS="$(TARGET_CXXFLAGS)" \
 		-device-option EGLFS_PLATFORM_HOOKS_SOURCES="$(QT5BASE_EGLFS_PLATFORM_HOOKS_SOURCES)" \