package/gstreamer/gst-ffmpeg: re-enable package when gcc bug 85180 is present

With Microblaze Gcc version < 8.x the build hangs to gcc bug 85180:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85180. This package has
been excluded from building if the toolchain is affected by gcc bug
85180. To be consistent with how we deal with this issue in other
packages, we re-enable the package and instead work around the issue
by building with -O0, since gcc bug 85180 manifests itself only when
optimization is enabled.

To achieve this:

- add --disable-optimizations to EXTRA_OPTS, which gets passed down to
  the built-in libav library
- pass -O0 to CFLAGS in CONF_ENV

Then we remove 'depends on !BR2_TOOLCHAIN_HAS_GCC_BUG_85180' and its
comment if not available from Config.in

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
[Thomas: tweak CFLAGS logic, improve commit log]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/gstreamer/gst-ffmpeg/Config.in

@@ -5,7 +5,6 @@ config BR2_PACKAGE_GST_FFMPEG
 	depends on !BR2_MIPS_CPU_MIPS32R6 && !BR2_MIPS_CPU_MIPS64R6
 	# triggers https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65151 on sh
 	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_5 || !BR2_sh
-	depends on !BR2_TOOLCHAIN_HAS_GCC_BUG_85180
 	select BR2_PACKAGE_GST_PLUGINS_BASE
 	help
 	  GStreamer plugin containing one plugin with a set of
@@ -29,6 +28,3 @@ endif
 
 comment "gst-ffmpeg needs a toolchain w/ gcc >= 5"
 	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_5 && BR2_sh
-
-comment "gst-ffmpeg needs a toolchain not affected by GCC bug 85180"
-	depends on BR2_TOOLCHAIN_HAS_GCC_BUG_85180

package/gstreamer/gst-ffmpeg/gst-ffmpeg.mk

@@ -90,6 +90,14 @@ ifeq ($(BR2_STATIC_LIBS),)
 GST_FFMPEG_CONF_EXTRA_OPTS += --enable-pic
 endif
 
+GST_FFMPEG_CFLAGS = $(TARGET_CFLAGS)
+
+ifeq ($(BR2_TOOLCHAIN_HAS_GCC_BUG_85180),y)
+GST_FFMPEG_CONF_EXTRA_OPTS += --disable-optimizations
+GST_FFMPEG_CFLAGS += -O0
+endif
+
+GST_FFMPEG_CONF_ENV += CFLAGS="$(GST_FFMPEG_CFLAGS)"
 GST_FFMPEG_CONF_OPTS += --with-ffmpeg-extra-configure="$(GST_FFMPEG_CONF_EXTRA_OPTS)"
 
 $(eval $(autotools-package))