Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10'

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

third_party/nix/tests/gc-concurrent.builder.sh

@@ -0,0 +1,13 @@
+mkdir $out
+echo $(cat $input1/foo)$(cat $input2/bar) > $out/foobar
+
+sleep 10
+
+# $out should not have been GC'ed while we were sleeping, but just in
+# case...
+mkdir -p $out
+
+# Check that the GC hasn't deleted the lock on our output.
+test -e "$out.lock"
+
+ln -s $input2 $out/input-2