findTarball: Handle pipefail

It was failing because the bash subshell died with SIGPIPE, which is
no longer ignored.

http://hydra.nixos.org/build/16766452

pkgs/build-support/release/ant-build.nix

@@ -108,7 +108,7 @@ stdenv.mkDerivation (
       . ${./functions.sh}
 
       origSrc=$src
-      src=$(findTarballs $src | head -1)
+      src=$(findTarball $src)
     ''; 
   }
 )

pkgs/build-support/release/binary-tarball.nix

@@ -38,7 +38,7 @@ stdenv.mkDerivation (
       . ${./functions.sh}
 
       origSrc=$src
-      src=$(findTarballs $src | head -1)
+      src=$(findTarball $src)
 
       if test -e $origSrc/nix-support/hydra-release-name; then
           releaseName=$(cat $origSrc/nix-support/hydra-release-name)

pkgs/build-support/release/debian-build.nix

@@ -32,7 +32,7 @@ vmTools.runInLinuxImage (stdenv.mkDerivation (
     postHook = ''
       . ${./functions.sh}
       propagateImageName
-      src=$(findTarballs $src | head -1) # Find a tarball.
+      src=$(findTarball $src)
     '';
 
     installExtraDebsPhase = ''

pkgs/build-support/release/functions.sh

@@ -1,11 +1,16 @@
-findTarballs() {
+findTarball() {
     local suffix i
-    test -d "$1/tarballs/" && {
+    if [ -f "$1" ]; then
+        echo "$1"
+        return
+    fi
+    if [ -d "$1/tarballs/" ]; then
         for suffix in tar.gz tgz tar.bz2 tbz2 tar.xz tar.lzma; do
-            for i in $1/tarballs/*.$suffix; do echo $i; done
-        done | sort
-    }
-    echo "$1"
+            for i in $1/tarballs/*.$suffix; do echo $i; return; done
+        done | sort | head -1
+        return
+    fi
+    return 1
 }
 
 canonicalizeJarManifest() {

pkgs/build-support/release/nix-build.nix

@@ -89,7 +89,7 @@ stdenv.mkDerivation (
     postHook = ''
       . ${./functions.sh}
       origSrc=$src
-      src=$(findTarballs $src | head -1)
+      src=$(findTarball $src)
     '';
 
     preHook = ''

pkgs/build-support/release/rpm-build.nix

@@ -16,7 +16,7 @@ vmTools.buildRPM (
     preBuild = ''
       . ${./functions.sh}
       propagateImageName
-      src=$(findTarballs $src | head -1) # Pick the first tarball.
+      src=$(findTarball $src)
     '';
 
     postInstall = ''