package/qt5base: fix race with libxkbcommon

qt5wayland package currently has a bug if the xkbcommon Qt config is not
enabled which highlighted a race issues between qt5base, libxkbcommon
and qt5wayland.

qt5wayland has a dependency on libxkbcommon package if it's enabled.
qt5base only has a dependency on libxkbcommon if xcb support is to be
enabled.

If libxkbcommon package is built before qt5base, qt5base will detect it
during its configure step and enable the Qt config accordingly. This
will make it available to qt5wayland afterwards, even if xcb support is
not enabled in Buildroot Kconfig.

However, if qt5base is built before libxkbcommon is, qt5base will not
advertise support of xbcommon feature to qt5wayland (which will fail its
build because of a bug in the source code).

Since the package build order should not impact the outcome of the
build, let's explicit the dependency if and only if libxkbcommon package
is to be compiled at some point in time so that at least this feature is
not susceptible to races.

Move the xkbcommon entries out of the BR2_PACKAGE_QT5BASE_XCB condition,
instead make them depend on BR2_PACKAGE_LIBXKBCOMMON. Since
BR2_PACKAGE_QT5BASE_XCB selects BR2_PACKAGE_LIBXKBCOMMON they are still
included if xcb is selected.

Cc: Quentin Schulz <foss+buildroot@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
[Arnout: remove the already existing xkbcommon entries]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/qt5/qt5base/qt5base.mk

@@ -174,9 +174,13 @@ QT5BASE_CONFIGURE_OPTS += $(if $(BR2_PACKAGE_QT5BASE_LINUXFB),--enable-linuxfb,-
 QT5BASE_CONFIGURE_OPTS += $(if $(BR2_PACKAGE_QT5BASE_DIRECTFB),-directfb,-no-directfb)
 QT5BASE_DEPENDENCIES   += $(if $(BR2_PACKAGE_QT5BASE_DIRECTFB),directfb)
 
+ifeq ($(BR2_PACKAGE_LIBXKBCOMMON),y)
+QT5BASE_CONFIGURE_OPTS += -xkbcommon
+QT5BASE_DEPENDENCIES   += libxkbcommon
+endif
+
 ifeq ($(BR2_PACKAGE_QT5BASE_XCB),y)
 QT5BASE_CONFIGURE_OPTS += -xcb
-QT5BASE_CONFIGURE_OPTS += -xkbcommon
 
 QT5BASE_DEPENDENCIES   += \
 	libxcb \
@@ -184,8 +188,7 @@ QT5BASE_DEPENDENCIES   += \
 	xcb-util-image \
 	xcb-util-keysyms \
 	xcb-util-renderutil \
-	xlib_libX11 \
-	libxkbcommon
+	xlib_libX11
 ifeq ($(BR2_PACKAGE_QT5BASE_WIDGETS),y)
 QT5BASE_DEPENDENCIES   += xlib_libXext
 endif