Auto merge of #22474 - iKevinY:pandoc-version-check, r=brson
Auto merge of #22474 - iKevinY:pandoc-version-check, r=brson

Executing `configure` seems to create the following error due to how the script [parses Pandoc's version](https://github.com/rust-lang/rust/blob/master/configure#L705):

```text
./configure: line 705: [: pandoc: integer expression expected
./configure: line 705: [: 1.12.4.2: integer expression expected
```

This issue seems to stem from a discrepancy between BSD and GNU versions of sed. This patch changes the sed command to use an extended regex, which works with both flavours of sed.

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