package/bullet: re-enable package when gcc bug 85180 is present

package/bullet: re-enable package when gcc bug 85180 is present

With Microblaze Gcc version < 8.x the build hangs due to gcc bug
85180: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85180. This
package has been excluded from building on Microblaze due to this.

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 pass -O0 in CMAKE_CXX_FLAGS and remove 'depends on
!BR2_microblaze' and its comment if not available from Config.in.

Note that the comment was talking about gcc bug 68476, but this gcc
bug is a duplicate of 85180. Since all Buildroot packages now use the
reference to gcc bug 85180 and the option is named
BR2_TOOLCHAIN_HAS_GCC_BUG_85180, we use this naming as well for
bullet.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>