chore: improve UX of build w/o API (#2265)
chore: improve UX of build w/o API (#2265)

Just do a full build if no API docs currently exist rather than
building the site and then aborting with an error message at the end of
it all.
NoahLuftYang/angular-ko,rsreimer/angular.io,rsreimer/angular.io,IdeaBlade/angular.io,realappie/angular.io,angular/angular-es,rsreimer/angular.io,angular/angular-ko,SaloGala/angular-es,angular/angular.io,Urigo/angular.io,juleskremer/angular.io,IdeaBlade/angular.io,Urigo/angular.io,kwalrath/angular.io,angular/angular.io,kwalrath/angular.io,gyujincho/angular-ko,chalin/angular.io,gyujincho/angular-ko,chalin/angular.io,kwalrath/angular.io,angular/angular-es,angular/angular-ko,NoahLuftYang/angular-ko,angular/angular-cn,IdeaBlade/angular.io,juleskremer/angular.io,SaloGala/angular-es,realappie/angular.io,GuzmanPI/angular-es,SaloGala/angular-es,realappie/angular.io,NoahLuftYang/angular-ko,gyujincho/angular-ko,angular/angular-cn,onyoon7/angular-ko,GuzmanPI/angular-es,Urigo/angular.io,angular/angular.io,Urigo/angular.io,Urigo/angular.io,kwalrath/angular.io,GuzmanPI/angular-es,GuzmanPI/angular-es,angular/angular-es,rsreimer/angular.io,angular/angular-es,angular/angular-ko,chalin/angular.io,angular/angular-cn,angular/angular.io,angular/angular-ko,realappie/angular.io,juleskremer/angular.io,GuzmanPI/angular-es,rsreimer/angular.io,IdeaBlade/angular.io,NoahLuftYang/angular-ko,SaloGala/angular-es,angular/angular-es,onyoon7/angular-ko,kwalrath/angular.io,gyujincho/angular-ko,IdeaBlade/angular.io,juleskremer/angular.io,gyujincho/angular-ko,angular/angular-cn,onyoon7/angular-ko,onyoon7/angular-ko,angular/angular-ko,NoahLuftYang/angular-ko,chalin/angular.io,chalin/angular.io,juleskremer/angular.io,angular/angular-cn,realappie/angular.io,SaloGala/angular-es,onyoon7/angular-ko,angular/angular.io