Error out if no src files are provided to Groovy
Error out if no src files are provided to Groovy

Otherwise you get groovyc's usage message spammed to stdout

--
Change-Id: I04bcfd9166adb6c9287839035f025f93d805e738
Reviewed-on: https://bazel-review.googlesource.com/#/c/2251/
MOS_MIGRATED_REVID=106693428

Digas29/bazel,perezd/bazel,whuwxl/bazel,davidzchen/bazel,aehlig/bazel,mbrukman/bazel,kamalmarhubi/bazel,mrdomino/bazel,whuwxl/bazel,iamthearm/bazel,hhclam/bazel,Digas29/bazel,iamthearm/bazel,dslomov/bazel,ulfjack/bazel,ulfjack/bazel,spxtr/bazel,cushon/bazel,rohitsaboo/bazel,ButterflyNetwork/bazel,mikelikespie/bazel,perezd/bazel,kchodorow/bazel,rohitsaboo/bazel,hhclam/bazel,dslomov/bazel,Asana/bazel,mikelikespie/bazel,spxtr/bazel,dinowernli/bazel,bazelbuild/bazel,hhclam/bazel,spxtr/bazel,dropbox/bazel,anupcshan/bazel,dinowernli/bazel,ButterflyNetwork/bazel,kchodorow/bazel-1,rohitsaboo/bazel,akira-baruah/bazel,safarmer/bazel,rohitsaboo/bazel,ButterflyNetwork/bazel,kchodorow/bazel,twitter-forks/bazel,iamthearm/bazel,ButterflyNetwork/bazel,LuminateWireless/bazel,abergmeier-dsfishlabs/bazel,hhclam/bazel,damienmg/bazel,werkt/bazel,snnn/bazel,twitter-forks/bazel,dslomov/bazel-windows,Digas29/bazel,dropbox/bazel,mbrukman/bazel,katre/bazel,iamthearm/bazel,katre/bazel,zhexuany/bazel,dslomov/bazel-windows,cushon/bazel,anupcshan/bazel,akira-baruah/bazel,damienmg/bazel,dslomov/bazel,werkt/bazel,spxtr/bazel,bazelbuild/bazel,perezd/bazel,juhalindfors/bazel-patches,bazelbuild/bazel,kchodorow/bazel,variac/bazel,twitter-forks/bazel,dslomov/bazel-windows,Digas29/bazel,anupcshan/bazel,mrdomino/bazel,dslomov/bazel,LuminateWireless/bazel,kchodorow/bazel,whuwxl/bazel,perezd/bazel,bazelbuild/bazel,akira-baruah/bazel,aehlig/bazel,snnn/bazel,mrdomino/bazel,iamthearm/bazel,abergmeier-dsfishlabs/bazel,mrdomino/bazel,zhexuany/bazel,anupcshan/bazel,spxtr/bazel,twitter-forks/bazel,werkt/bazel,mbrukman/bazel,spxtr/bazel,mikelikespie/bazel,kchodorow/bazel,spxtr/bazel,dropbox/bazel,dropbox/bazel,LuminateWireless/bazel,ulfjack/bazel,UrbanCompass/bazel,aehlig/bazel,juhalindfors/bazel-patches,zhexuany/bazel,variac/bazel,aehlig/bazel,cushon/bazel,hermione521/bazel,katre/bazel,davidzchen/bazel,LuminateWireless/bazel,davidzchen/bazel,akira-baruah/bazel,bazelbuild/bazel,safarmer/bazel,ulfjack/bazel,damienmg/bazel,juhalindfors/bazel-patches,Asana/bazel,Digas29/bazel,mrdomino/bazel,anupcshan/bazel,hermione521/bazel,zhexuany/bazel,Asana/bazel,davidzchen/bazel,perezd/bazel,LuminateWireless/bazel,damienmg/bazel,kchodorow/bazel,LuminateWireless/bazel,safarmer/bazel,hermione521/bazel,ulfjack/bazel,aehlig/bazel,kamalmarhubi/bazel,mbrukman/bazel,abergmeier-dsfishlabs/bazel,snnn/bazel,twitter-forks/bazel,twitter-forks/bazel,variac/bazel,hermione521/bazel,mikelikespie/bazel,ButterflyNetwork/bazel,abergmeier-dsfishlabs/bazel,kchodorow/bazel-1,akira-baruah/bazel,meteorcloudy/bazel,cushon/bazel,katre/bazel,twitter-forks/bazel,hermione521/bazel,kamalmarhubi/bazel,variac/bazel,damienmg/bazel,meteorcloudy/bazel,perezd/bazel,mikelalcon/bazel,variac/bazel,whuwxl/bazel,werkt/bazel,whuwxl/bazel,kchodorow/bazel-1,damienmg/bazel,bazelbuild/bazel,meteorcloudy/bazel,ulfjack/bazel,mikelalcon/bazel,Asana/bazel,juhalindfors/bazel-patches,mikelalcon/bazel,dslomov/bazel-windows,UrbanCompass/bazel,whuwxl/bazel,mikelikespie/bazel,werkt/bazel,mrdomino/bazel,dslomov/bazel,mbrukman/bazel,cushon/bazel,dinowernli/bazel,ButterflyNetwork/bazel,rohitsaboo/bazel,UrbanCompass/bazel,kchodorow/bazel-1,kamalmarhubi/bazel,dslomov/bazel,meteorcloudy/bazel,dinowernli/bazel,kchodorow/bazel-1,kchodorow/bazel,meteorcloudy/bazel,kamalmarhubi/bazel,UrbanCompass/bazel,variac/bazel,Asana/bazel,dropbox/bazel,aehlig/bazel,safarmer/bazel,abergmeier-dsfishlabs/bazel,iamthearm/bazel,perezd/bazel,Digas29/bazel,zhexuany/bazel,variac/bazel,mikelikespie/bazel,meteorcloudy/bazel,Asana/bazel,Asana/bazel,hermione521/bazel,safarmer/bazel,katre/bazel,snnn/bazel,dslomov/bazel,mbrukman/bazel,juhalindfors/bazel-patches,davidzchen/bazel,safarmer/bazel,snnn/bazel,mikelalcon/bazel,dslomov/bazel-windows,zhexuany/bazel,dropbox/bazel,kamalmarhubi/bazel,snnn/bazel,juhalindfors/bazel-patches,dinowernli/bazel,UrbanCompass/bazel,cushon/bazel,hhclam/bazel,damienmg/bazel,mikelalcon/bazel,davidzchen/bazel,werkt/bazel,aehlig/bazel,akira-baruah/bazel,dinowernli/bazel,abergmeier-dsfishlabs/bazel,juhalindfors/bazel-patches,ulfjack/bazel,hhclam/bazel,katre/bazel,kchodorow/bazel-1,mikelalcon/bazel,snnn/bazel,UrbanCompass/bazel,meteorcloudy/bazel,davidzchen/bazel,rohitsaboo/bazel,anupcshan/bazel,dslomov/bazel-windows