fix(@ngtools/webpack): don't use src dir as a resource
fix(@ngtools/webpack): don't use src dir as a resource

We add either `src/` or `src/$$_gendir/` directories as the lazy route resource, which causes rebuilds whenever anything changes there.

This PR makes it always use the `src/$$_gendir/` special directory.

@brocco this should also fix your local failing poll test.

Fix #6238
Close #6959

clydin/angular-cli,Brocco/angular-cli,nickroberts/angular-cli,angular/angular-cli,filipesilva/angular-cli,nwronski/angular-cli,clydin/angular-cli,mham/angular-cli,DevIntent/angular-cli,clydin/angular-cli,hansl/angular-cli,nickroberts/angular-cli,garoyeri/angular-cli,maxime1992/angular-cli,ocombe/angular-cli,manekinekko/angular-cli,dzonatan/angular-cli,geofffilippi/angular-cli,pedroapy/angular-cli,DevIntent/angular-cli,escorp/angular-cli,manekinekko/angular-cli,geofffilippi/angular-cli,escorp/angular-cli,garoyeri/angular-cli,pedroapy/angular-cli,beeman/angular-cli,mham/angular-cli,ocombe/angular-cli,hansl/angular-cli,DevIntent/angular-cli,hansl/angular-cli,angular/angular-cli,mham/angular-cli,DevIntent/angular-cli,filipesilva/angular-cli,Brocco/angular-cli,DevIntent/angular-cli,filipesilva/angular-cli,maxime1992/angular-cli,beeman/angular-cli,catull/angular-cli,pedroapy/angular-cli,catull/angular-cli,dzonatan/angular-cli,geofffilippi/angular-cli,nwronski/angular-cli,ocombe/angular-cli,nwronski/angular-cli,escorp/angular-cli,RicardoVaranda/angular-cli,nickroberts/angular-cli,garoyeri/angular-cli,angular/angular-cli,geofffilippi/angular-cli,Brocco/angular-cli,angular/angular-cli,clydin/angular-cli,ocombe/angular-cli,ocombe/angular-cli,catull/angular-cli,Brocco/angular-cli,manekinekko/angular-cli,beeman/angular-cli,dzonatan/angular-cli,beeman/angular-cli,maxime1992/angular-cli,RicardoVaranda/angular-cli,RicardoVaranda/angular-cli,Brocco/angular-cli,catull/angular-cli,hansl/angular-cli,filipesilva/angular-cli