libunwind: Fix build on arm < v6
libunwind: Fix build on arm < v6

atomics that are needed for libunuwind are not available on
arm < v6

Fixes errors like

| ../src/.libs/libunwind.so: error: undefined reference to
'AO_fetch_and_add1'
| ../src/.libs/libunwind.so: error: undefined reference to
'AO_fetch_and_add'
| collect2: error: ld returned 1 exit status

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>
Signed-off-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@gmail.com>

RedFIR/meta-openembedded,dm8tbr/kodi-wip,schnitzeltony/meta-openembedded,epylar/meta-openembedded,schnitzeltony/meta-openembedded,kraj/meta-openembedded,rdm-dev/meta-openembedded,mrchapp/meta-openembedded,rofehr/meta-openembedded,dongkc/meta-openembedded,shr-distribution/meta-oe,victronenergy/meta-openembedded,shr-distribution/meta-oe,victronenergy/meta-openembedded,rdm-dev/meta-openembedded,victronenergy/meta-openembedded,dm8tbr/kodi-wip,MCherifiOSS/meta-openembedded,schnitzeltony/meta-openembedded,kraj/meta-openembedded,shr-distribution/meta-oe,mrchapp/meta-openembedded,shr-distribution/meta-oe,moto-timo/meta-openembedded,openembedded/meta-openembedded,joelagnel/meta-openembedded,mrchapp/meta-openembedded,MCherifiOSS/meta-openembedded,trikset/meta-openembedded,kraj/meta-openembedded,RealVNC/yocto_imx6sabreauto_meta-openembedded,RealDigitalMedia/meta-openembedded,RedFIR/meta-openembedded,trikset/meta-openembedded,epylar/meta-openembedded,trikset/meta-openembedded,moto-timo/meta-openembedded,fredcadete/meta-openembedded,tobw/meta-openembedded,shr-distribution/meta-oe,dm8tbr/kodi-wip,RealVNC/yocto_imx6sabreauto_meta-openembedded,akuster/meta-openembedded,trikset/meta-openembedded,fredcadete/meta-openembedded,RealDigitalMedia/meta-openembedded,rehsack/meta-openembedded,openembedded/meta-openembedded,mrchapp/meta-openembedded,openembedded/meta-openembedded,RedFIR/meta-openembedded,fredcadete/meta-openembedded,dongkc/meta-openembedded,tobw/meta-openembedded,trikset/meta-openembedded,VCTLabs/meta-openembedded,victronenergy/meta-openembedded,MCherifiOSS/meta-openembedded,joelagnel/meta-openembedded,trikset/meta-openembedded,amery/meta-openembedded,tobw/meta-openembedded,openembedded/meta-openembedded,joelagnel/meta-openembedded,openembedded/meta-openembedded,tobw/meta-openembedded,akuster/meta-openembedded,moto-timo/meta-openembedded,RealDigitalMedia/meta-openembedded,rehsack/meta-openembedded,RealVNC/yocto_imx6sabreauto_meta-openembedded,VCTLabs/meta-openembedded,rofehr/meta-openembedded,rdm-dev/meta-openembedded,RedFIR/meta-openembedded,RedFIR/meta-openembedded,dm8tbr/kodi-wip,amery/meta-openembedded,epylar/meta-openembedded,VCTLabs/meta-openembedded,fredcadete/meta-openembedded,kraj/meta-openembedded,martiert/meta-openembedded,rehsack/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,rdm-dev/meta-openembedded,joelagnel/meta-openembedded,RealVNC/yocto_imx6sabreauto_meta-openembedded,lgirdk/meta-openembedded,schnitzeltony/meta-openembedded,amery/meta-openembedded,MCherifiOSS/meta-openembedded,dm8tbr/kodi-wip,rdm-dev/meta-openembedded,epylar/meta-openembedded,VCTLabs/meta-openembedded,martiert/meta-openembedded,akuster/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,joelagnel/meta-openembedded,kraj/meta-openembedded,epylar/meta-openembedded,rofehr/meta-openembedded,fredcadete/meta-openembedded,lixinfnst/meta-openembedded,lgirdk/meta-openembedded,dm8tbr/kodi-wip,openembedded/meta-openembedded,victronenergy/meta-openembedded,amery/meta-openembedded,VCTLabs/meta-openembedded,lgirdk/meta-openembedded,moto-timo/meta-openembedded,epylar/meta-openembedded,amery/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,RedFIR/meta-openembedded,lixinfnst/meta-openembedded,rofehr/meta-openembedded,lixinfnst/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,rdm-dev/meta-openembedded,RealVNC/yocto_imx6sabreauto_meta-openembedded,lgirdk/meta-openembedded,joelagnel/meta-openembedded,joelagnel/meta-openembedded,epylar/meta-openembedded,RedFIR/meta-openembedded,dongkc/meta-openembedded,kraj/meta-openembedded,lgirdk/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,RealDigitalMedia/meta-openembedded,victronenergy/meta-openembedded,trikset/meta-openembedded,mrchapp/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,shr-distribution/meta-oe,rehsack/meta-openembedded,MCherifiOSS/meta-openembedded,rofehr/meta-openembedded,martiert/meta-openembedded,amery/meta-openembedded,rdm-dev/meta-openembedded,fredcadete/meta-openembedded,mrchapp/meta-openembedded,akuster/meta-openembedded,lgirdk/meta-openembedded,VCTLabs/meta-openembedded,akuster/meta-openembedded,amery/meta-openembedded,dongkc/meta-openembedded,martiert/meta-openembedded,martiert/meta-openembedded,schnitzeltony/meta-openembedded,schnitzeltony/meta-openembedded,openembedded/meta-openembedded,rofehr/meta-openembedded,kraj/meta-openembedded,dm8tbr/kodi-wip,lgirdk/meta-openembedded,rehsack/meta-openembedded,amery/meta-openembedded,VCTLabs/meta-openembedded,rofehr/meta-openembedded,sigma-embedded/elito-org.openembedded.meta,tobw/meta-openembedded,openembedded/meta-openembedded,epylar/meta-openembedded,rehsack/meta-openembedded,lixinfnst/meta-openembedded,shr-distribution/meta-oe,dongkc/meta-openembedded,RedFIR/meta-openembedded,joelagnel/meta-openembedded,mrchapp/meta-openembedded,fredcadete/meta-openembedded,shr-distribution/meta-oe,fredcadete/meta-openembedded,rehsack/meta-openembedded,victronenergy/meta-openembedded,tobw/meta-openembedded,dm8tbr/kodi-wip,VCTLabs/meta-openembedded,moto-timo/meta-openembedded,MCherifiOSS/meta-openembedded,rdm-dev/meta-openembedded,RealDigitalMedia/meta-openembedded,rofehr/meta-openembedded,lixinfnst/meta-openembedded,trikset/meta-openembedded,lixinfnst/meta-openembedded,schnitzeltony/meta-openembedded