package/belle-sip: fix build failure due to gcc bug 99410

package/belle-sip: fix build failure due to gcc bug 99410

The belle-sip package exhibits gcc bug 99410 when built for the Nios2
architecture with optimization enabled, which causes a build failure.

As done for other packages in Buildroot work around this gcc bug by
setting optimization to -O0 if BR2_TOOLCHAIN_HAS_GCC_BUG_99410=y.

Fixes:
http://autobuild.buildroot.net/results/71f26fd81db8e9b19b3f18f3f3cefd9c768f094f/

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>