ffmpeg: let the user override the --cpu value

Grab the content of BR2_PACKAGE_FFMPEG_EXTRACONF after guessing the CPU,
so the user will still have the possibility to override it.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Reviewed-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/ffmpeg/ffmpeg.mk

@@ -444,14 +444,14 @@ else
 FFMPEG_CONF_OPTS += --disable-pic
 endif
 
-FFMPEG_CONF_OPTS += $(call qstrip,$(BR2_PACKAGE_FFMPEG_EXTRACONF))
-
 ifneq ($(call qstrip,$(BR2_GCC_TARGET_CPU)),)
 FFMPEG_CONF_OPTS += --cpu=$(BR2_GCC_TARGET_CPU)
 else ifneq ($(call qstrip,$(BR2_GCC_TARGET_ARCH)),)
 FFMPEG_CONF_OPTS += --cpu=$(BR2_GCC_TARGET_ARCH)
 endif
 
+FFMPEG_CONF_OPTS += $(call qstrip,$(BR2_PACKAGE_FFMPEG_EXTRACONF))
+
 # Override FFMPEG_CONFIGURE_CMDS: FFmpeg does not support --target and others
 define FFMPEG_CONFIGURE_CMDS
 	(cd $(FFMPEG_SRCDIR) && rm -rf config.cache && \