Merge pull request #112421 from sternenseemann/fetchcvs-fix-missing-env

fetchcvs: fix ssh wrapper failing due to missing /usr/bin/env

pkgs/build-support/fetchcvs/builder.sh

@@ -1,6 +1,6 @@
 source $stdenv/setup
 
-(echo '#!/usr/bin/env sh'; \
+(echo "#!$SHELL"; \
  echo 'ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no "$@"') > ssh
 chmod +x ssh
 export CVS_RSH=$PWD/ssh