Unconditionally disable LLVM's FastISel on AArch64
Unconditionally disable LLVM's FastISel on AArch64

Before ca07e256f62f772d14c42f41af46f2aeacc54983, LLVM's AArch64FastISel
had a sign (and zero?) extension bug. Until rustc gets its LLVM past
that commit, the way of workaround is to pass an option to LLVM that
forces the disabling of FastISel (which would normally kick in for -O0).

Fixes #21627

krzysz00/rust,mvdnes/rust,ebfull/rust,graydon/rust,AerialX/rust,KokaKiwi/rust,avdi/rust,mahkoh/rust,mdinger/rust,jroesch/rust,mvdnes/rust,XMPPwocky/rust,victorvde/rust,mvdnes/rust,jashank/rust,mvdnes/rust,pelmers/rust,andars/rust,vhbit/rust,l0kod/rust,robertg/rust,avdi/rust,KokaKiwi/rust,XMPPwocky/rust,reem/rust,gifnksm/rust,carols10cents/rust,pshc/rust,richo/rust,GBGamer/rust,andars/rust,vhbit/rust,rprichard/rust,andars/rust,jashank/rust,jroesch/rust,ejjeong/rust,kwantam/rust,omasanori/rust,graydon/rust,vhbit/rust,ruud-v-a/rust,nwin/rust,cllns/rust,ejjeong/rust,miniupnp/rust,seanrivera/rust,aidancully/rust,pelmers/rust,hauleth/rust,krzysz00/rust,seanrivera/rust,carols10cents/rust,bombless/rust,philyoon/rust,kwantam/rust,aidancully/rust,hauleth/rust,hauleth/rust,philyoon/rust,victorvde/rust,nwin/rust,aepsil0n/rust,zaeleus/rust,vhbit/rust,victorvde/rust,mdinger/rust,aepsil0n/rust,ejjeong/rust,l0kod/rust,XMPPwocky/rust,ruud-v-a/rust,TheNeikos/rust,jroesch/rust,rprichard/rust,krzysz00/rust,kwantam/rust,dwillmer/rust,untitaker/rust,aepsil0n/rust,sae-bom/rust,GBGamer/rust,AerialX/rust-rt-minimal,jashank/rust,jashank/rust,carols10cents/rust,andars/rust,nwin/rust,vhbit/rust,untitaker/rust,aneeshusa/rust,reem/rust,l0kod/rust,pshc/rust,ebfull/rust,avdi/rust,avdi/rust,aidancully/rust,mahkoh/rust,jashank/rust,cllns/rust,bombless/rust,robertg/rust,miniupnp/rust,AerialX/rust,l0kod/rust,untitaker/rust,l0kod/rust,omasanori/rust,zubron/rust,aepsil0n/rust,l0kod/rust,aneeshusa/rust,aidancully/rust,reem/rust,zubron/rust,pshc/rust,aidancully/rust,GBGamer/rust,philyoon/rust,rohitjoshi/rust,nwin/rust,AerialX/rust,GBGamer/rust,ebfull/rust,cllns/rust,mvdnes/rust,pelmers/rust,aepsil0n/rust,ejjeong/rust,dwillmer/rust,seanrivera/rust,zubron/rust,KokaKiwi/rust,cllns/rust,kwantam/rust,omasanori/rust,KokaKiwi/rust,untitaker/rust,omasanori/rust,mdinger/rust,mdinger/rust,dwillmer/rust,hauleth/rust,rprichard/rust,gifnksm/rust,kwantam/rust,krzysz00/rust,andars/rust,GBGamer/rust,jroesch/rust,ebfull/rust,AerialX/rust-rt-minimal,pshc/rust,bombless/rust,AerialX/rust,TheNeikos/rust,pshc/rust,sae-bom/rust,zachwick/rust,bombless/rust,richo/rust,ruud-v-a/rust,GBGamer/rust,aneeshusa/rust,XMPPwocky/rust,TheNeikos/rust,philyoon/rust,philyoon/rust,mvdnes/rust,AerialX/rust-rt-minimal,zachwick/rust,AerialX/rust,GBGamer/rust,KokaKiwi/rust,aneeshusa/rust,avdi/rust,robertg/rust,dwillmer/rust,ruud-v-a/rust,zubron/rust,miniupnp/rust,mahkoh/rust,carols10cents/rust,zachwick/rust,rprichard/rust,zaeleus/rust,pelmers/rust,graydon/rust,seanrivera/rust,krzysz00/rust,bombless/rust,miniupnp/rust,aneeshusa/rust,dwillmer/rust,cllns/rust,miniupnp/rust,robertg/rust,zubron/rust,omasanori/rust,nwin/rust,reem/rust,rprichard/rust,rohitjoshi/rust,vhbit/rust,l0kod/rust,zachwick/rust,omasanori/rust,miniupnp/rust,victorvde/rust,mihneadb/rust,victorvde/rust,ejjeong/rust,ejjeong/rust,gifnksm/rust,mihneadb/rust,jashank/rust,AerialX/rust,pelmers/rust,avdi/rust,mahkoh/rust,pshc/rust,richo/rust,victorvde/rust,reem/rust,aneeshusa/rust,nwin/rust,carols10cents/rust,mdinger/rust,AerialX/rust-rt-minimal,GBGamer/rust,jroesch/rust,zaeleus/rust,untitaker/rust,zaeleus/rust,TheNeikos/rust,dwillmer/rust,jashank/rust,hauleth/rust,KokaKiwi/rust,kwantam/rust,robertg/rust,reem/rust,mihneadb/rust,aidancully/rust,richo/rust,hauleth/rust,sae-bom/rust,TheNeikos/rust,AerialX/rust-rt-minimal,seanrivera/rust,graydon/rust,mdinger/rust,richo/rust,krzysz00/rust,carols10cents/rust,jroesch/rust,bombless/rust,rohitjoshi/rust,sae-bom/rust,zubron/rust,ruud-v-a/rust,andars/rust,mahkoh/rust,TheNeikos/rust,jashank/rust,jroesch/rust,zachwick/rust,aepsil0n/rust,nwin/rust,XMPPwocky/rust,gifnksm/rust,dwillmer/rust,mihneadb/rust,mihneadb/rust,rohitjoshi/rust,philyoon/rust,sae-bom/rust,rohitjoshi/rust,jroesch/rust,vhbit/rust,graydon/rust,mihneadb/rust,pshc/rust,sae-bom/rust,graydon/rust,cllns/rust,zubron/rust,ebfull/rust,AerialX/rust-rt-minimal,ebfull/rust,zaeleus/rust,ruud-v-a/rust,seanrivera/rust,l0kod/rust,dwillmer/rust,mahkoh/rust,gifnksm/rust,rohitjoshi/rust,zaeleus/rust,miniupnp/rust,miniupnp/rust,untitaker/rust,richo/rust,vhbit/rust,zachwick/rust,pelmers/rust,rprichard/rust,pshc/rust,nwin/rust,robertg/rust,zubron/rust,gifnksm/rust,XMPPwocky/rust