provision: Add symlink creation check.
provision: Add symlink creation check.

This helps automatically detect a common issue where users try to use
the Vagrant development environment on windows without administrator
permissions, which results in errors trying to create symlinks.

KingxBanana/zulip,zulip/zulip,zulip/zulip,jackrzhang/zulip,brainwane/zulip,vaidap/zulip,jackrzhang/zulip,verma-varsha/zulip,zacps/zulip,samatdav/zulip,sharmaeklavya2/zulip,calvinleenyc/zulip,samatdav/zulip,KingxBanana/zulip,zacps/zulip,Jianchun1/zulip,Jianchun1/zulip,verma-varsha/zulip,mahim97/zulip,dhcrzf/zulip,peguin40/zulip,Diptanshu8/zulip,jainayush975/zulip,arpith/zulip,ryanbackman/zulip,mahim97/zulip,kou/zulip,rishig/zulip,brainwane/zulip,isht3/zulip,cosmicAsymmetry/zulip,isht3/zulip,arpith/zulip,dattatreya303/zulip,vaidap/zulip,PhilSk/zulip,christi3k/zulip,Galexrt/zulip,Diptanshu8/zulip,samatdav/zulip,hackerkid/zulip,peguin40/zulip,rishig/zulip,jackrzhang/zulip,Juanvulcano/zulip,jphilipsen05/zulip,souravbadami/zulip,grave-w-grave/zulip,aakash-cr7/zulip,shubhamdhama/zulip,hackerkid/zulip,KingxBanana/zulip,aakash-cr7/zulip,ryanbackman/zulip,blaze225/zulip,isht3/zulip,AZtheAsian/zulip,samatdav/zulip,jrowan/zulip,timabbott/zulip,blaze225/zulip,shubhamdhama/zulip,JPJPJPOPOP/zulip,peguin40/zulip,calvinleenyc/zulip,brainwane/zulip,AZtheAsian/zulip,grave-w-grave/zulip,aakash-cr7/zulip,aakash-cr7/zulip,TigorC/zulip,blaze225/zulip,rht/zulip,isht3/zulip,hackerkid/zulip,arpith/zulip,jphilipsen05/zulip,cosmicAsymmetry/zulip,christi3k/zulip,dawran6/zulip,ryanbackman/zulip,grave-w-grave/zulip,samatdav/zulip,jrowan/zulip,vikas-parashar/zulip,sonali0901/zulip,Diptanshu8/zulip,cosmicAsymmetry/zulip,isht3/zulip,aakash-cr7/zulip,Jianchun1/zulip,zulip/zulip,niftynei/zulip,dattatreya303/zulip,jphilipsen05/zulip,vaidap/zulip,cosmicAsymmetry/zulip,verma-varsha/zulip,sharmaeklavya2/zulip,amyliu345/zulip,susansls/zulip,timabbott/zulip,sharmaeklavya2/zulip,SmartPeople/zulip,Juanvulcano/zulip,rht/zulip,dawran6/zulip,synicalsyntax/zulip,jrowan/zulip,punchagan/zulip,calvinleenyc/zulip,vaidap/zulip,grave-w-grave/zulip,sharmaeklavya2/zulip,souravbadami/zulip,reyha/zulip,JPJPJPOPOP/zulip,punchagan/zulip,susansls/zulip,andersk/zulip,timabbott/zulip,ryanbackman/zulip,verma-varsha/zulip,mahim97/zulip,rishig/zulip,TigorC/zulip,reyha/zulip,calvinleenyc/zulip,Jianchun1/zulip,jainayush975/zulip,SmartPeople/zulip,zacps/zulip,AZtheAsian/zulip,calvinleenyc/zulip,andersk/zulip,brockwhittaker/zulip,joyhchen/zulip,rht/zulip,dattatreya303/zulip,susansls/zulip,TigorC/zulip,dhcrzf/zulip,Galexrt/zulip,amyliu345/zulip,SmartPeople/zulip,cosmicAsymmetry/zulip,blaze225/zulip,eeshangarg/zulip,AZtheAsian/zulip,dattatreya303/zulip,j831/zulip,shubhamdhama/zulip,samatdav/zulip,dawran6/zulip,reyha/zulip,jphilipsen05/zulip,joyhchen/zulip,Jianchun1/zulip,KingxBanana/zulip,punchagan/zulip,dattatreya303/zulip,souravbadami/zulip,vaidap/zulip,niftynei/zulip,jphilipsen05/zulip,sonali0901/zulip,vikas-parashar/zulip,Galexrt/zulip,vikas-parashar/zulip,verma-varsha/zulip,brockwhittaker/zulip,dattatreya303/zulip,sharmaeklavya2/zulip,synicalsyntax/zulip,synicalsyntax/zulip,Juanvulcano/zulip,Jianchun1/zulip,j831/zulip,SmartPeople/zulip,joyhchen/zulip,vabs22/zulip,eeshangarg/zulip,brockwhittaker/zulip,Juanvulcano/zulip,christi3k/zulip,JPJPJPOPOP/zulip,jrowan/zulip,sonali0901/zulip,rishig/zulip,brockwhittaker/zulip,tommyip/zulip,eeshangarg/zulip,brockwhittaker/zulip,PhilSk/zulip,JPJPJPOPOP/zulip,amanharitsh123/zulip,kou/zulip,synicalsyntax/zulip,synicalsyntax/zulip,arpith/zulip,niftynei/zulip,peguin40/zulip,zacps/zulip,sharmaeklavya2/zulip,vikas-parashar/zulip,peguin40/zulip,tommyip/zulip,brainwane/zulip,dhcrzf/zulip,SmartPeople/zulip,reyha/zulip,ryanbackman/zulip,Diptanshu8/zulip,vabs22/zulip,rishig/zulip,vikas-parashar/zulip,jainayush975/zulip,isht3/zulip,vabs22/zulip,Juanvulcano/zulip,dawran6/zulip,eeshangarg/zulip,grave-w-grave/zulip,JPJPJPOPOP/zulip,hackerkid/zulip,jainayush975/zulip,jackrzhang/zulip,vabs22/zulip,Juanvulcano/zulip,punchagan/zulip,joyhchen/zulip,kou/zulip,dawran6/zulip,brainwane/zulip,AZtheAsian/zulip,andersk/zulip,zulip/zulip,rht/zulip,shubhamdhama/zulip,hackerkid/zulip,TigorC/zulip,j831/zulip,zulip/zulip,showell/zulip,PhilSk/zulip,punchagan/zulip,kou/zulip,vabs22/zulip,AZtheAsian/zulip,timabbott/zulip,christi3k/zulip,rht/zulip,susansls/zulip,showell/zulip,Diptanshu8/zulip,ryanbackman/zulip,TigorC/zulip,kou/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,niftynei/zulip,rishig/zulip,amanharitsh123/zulip,susansls/zulip,zulip/zulip,grave-w-grave/zulip,KingxBanana/zulip,joyhchen/zulip,jackrzhang/zulip,brainwane/zulip,timabbott/zulip,amanharitsh123/zulip,punchagan/zulip,jainayush975/zulip,amanharitsh123/zulip,blaze225/zulip,christi3k/zulip,reyha/zulip,Galexrt/zulip,sonali0901/zulip,amanharitsh123/zulip,niftynei/zulip,kou/zulip,sonali0901/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip,JPJPJPOPOP/zulip,timabbott/zulip,Galexrt/zulip,dawran6/zulip,timabbott/zulip,vaidap/zulip,souravbadami/zulip,niftynei/zulip,vikas-parashar/zulip,shubhamdhama/zulip,jrowan/zulip,shubhamdhama/zulip,aakash-cr7/zulip,Diptanshu8/zulip,jrowan/zulip,KingxBanana/zulip,tommyip/zulip,joyhchen/zulip,PhilSk/zulip,mahim97/zulip,showell/zulip,dhcrzf/zulip,j831/zulip,Galexrt/zulip,amyliu345/zulip,brockwhittaker/zulip,eeshangarg/zulip,mahim97/zulip,j831/zulip,mahim97/zulip,rht/zulip,susansls/zulip,calvinleenyc/zulip,amyliu345/zulip,sonali0901/zulip,j831/zulip,reyha/zulip,arpith/zulip,andersk/zulip,punchagan/zulip,TigorC/zulip,dhcrzf/zulip,synicalsyntax/zulip,showell/zulip,vabs22/zulip,dhcrzf/zulip,brainwane/zulip,synicalsyntax/zulip,jackrzhang/zulip,jainayush975/zulip,tommyip/zulip,tommyip/zulip,PhilSk/zulip,souravbadami/zulip,rishig/zulip,jackrzhang/zulip,cosmicAsymmetry/zulip,hackerkid/zulip,christi3k/zulip,souravbadami/zulip,verma-varsha/zulip,showell/zulip,kou/zulip,jphilipsen05/zulip,peguin40/zulip,zacps/zulip,amanharitsh123/zulip,dhcrzf/zulip,PhilSk/zulip,showell/zulip,zacps/zulip,blaze225/zulip,tommyip/zulip,shubhamdhama/zulip,amyliu345/zulip,Galexrt/zulip,tommyip/zulip,rht/zulip,SmartPeople/zulip,amyliu345/zulip,eeshangarg/zulip,showell/zulip,arpith/zulip