fix(tests/functional/repl): skip test if stack size limit is insufficient

Nix attempts to set the stack size to 64 MB during initialization, which is
required for the repl tests to run successfully. Skip the tests on systems
where the hard stack limit is less than this value rather than failing.

tests/functional/repl.sh

@@ -25,6 +25,13 @@ import $testDir/undefined-variable.nix
 
 TODO_NixOS
 
+# FIXME: repl tests fail on systems with stack limits
+stack_ulimit="$(ulimit -Hs)"
+stack_required="$((64 * 1024 * 1024))"
+if [[ "$stack_ulimit" != "unlimited" ]]; then
+    ((stack_ulimit < stack_required)) && skipTest "repl tests cannot run on systems with stack size <$stack_required ($stack_ulimit)"
+fi
+
 testRepl () {
     local nixArgs
     nixArgs=("$@")