lvgl: make libdrm include conditional

The libdrm include is only needed when "drm" is selected in
PACKAGECONFIG.

In addition, move the TARGET_CFLAG addition to lv-conf.inc, where the
DRM configuration is actually selected for LVGL.

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-graphics/lvgl/lv-conf.inc

@@ -2,6 +2,9 @@ PACKAGECONFIG[drm] = ",,libdrm"
 PACKAGECONFIG[fbdev] = ",,"
 PACKAGECONFIG[sdl] = ",,virtual/libsdl2 libsdl2-image"
 
+# Add libdrm include if drm is selected in PACKAGECONFIG
+TARGET_CFLAGS += "${@bb.utils.contains('PACKAGECONFIG', 'drm', '-I${STAGING_INCDIR}/libdrm', '', d)}"
+
 LVGL_CONFIG_USE_DRM = "${@bb.utils.contains('PACKAGECONFIG', 'drm', '1', '0', d)}"
 
 LVGL_CONFIG_USE_EVDEV = "${@bb.utils.contains_any('PACKAGECONFIG', 'drm fbdev', '1', '0', d)}"

meta-oe/recipes-graphics/lvgl/lvgl-demo-fb_9.0.0.bb

@@ -30,8 +30,6 @@ inherit cmake
 
 S = "${WORKDIR}/git"
 
-TARGET_CFLAGS += "-I${STAGING_INCDIR}/libdrm"
-
 do_configure:prepend() {
 	if [ "${LVGL_CONFIG_USE_SDL}" -eq 1 ] ; then
 		# Add libsdl build dependency, SDL2_image has no cmake file

meta-oe/recipes-graphics/lvgl/lvgl_9.0.0.bb

@@ -22,8 +22,6 @@ inherit cmake
 EXTRA_OECMAKE = "-DLIB_INSTALL_DIR=${baselib} -DBUILD_SHARED_LIBS=ON"
 S = "${WORKDIR}/git"
 
-TARGET_CFLAGS += "-I${STAGING_INCDIR}/libdrm"
-
 ALLOW_EMPTY:${PN} = "1"
 
 PACKAGECONFIG ??= "drm"