hydra: remove HYDRA_HOME env var, not used

release.nix

@@ -58,7 +58,6 @@ rec {
             wrapProgram $i \
                 --prefix PERL5LIB ':' $out/libexec/hydra/lib:$PERL5LIB \
                 --prefix PATH ':' $out/bin:$hydraPath \
-                --set HYDRA_HOME $out/libexec/hydra \
                 --set HYDRA_RELEASE ${tarball.version} \
                 --set NIX_RELEASE ${nix.name}
         done

src/script/hydra_queue_runner.pl.in

@@ -11,9 +11,6 @@ use Nix;
 chdir getHydraPath or die;
 my $db = openHydraDB;
 
-my $hydraHome = $ENV{"HYDRA_HOME"};
-die "The HYDRA_HOME environment variable is not set!\n" unless defined $hydraHome;
-
 STDOUT->autoflush();
 
 #$SIG{CHLD} = 'IGNORE';