[test/gold] Copy some more backtick test cases from issue #1449

Run like this:

    test/gold.sh test-autoconf-backtick

And then see _tmp/shebang.txt and _tmp/osh.txt.  (This reminds me the
test/gold.sh harness is a little wonky)

test/gold.sh

@@ -136,6 +136,11 @@ test-parse-help() {
   _compare $dir/excerpt.sh _parse_help ls
 }
 
+test-autoconf-backtick() {
+  # https://github.com/oilshell/oil/issues/1449
+  _compare $GOLD_DIR/autoconf-backtick.sh
+}
+
 # Gah, bash gets this from compile-time configuration generated with autoconf,
 # not uname().  It looks like 'linux-gnu' on Ubuntu.  In Alpine, it's
 # 'linux-musl'.

test/gold/autoconf-backtick.sh

@@ -0,0 +1,50 @@
+#! /bin/sh
+
+# From https://github.com/oilshell/oil/issues/1449
+
+set -e
+
+nargs () {
+    n_args=$#
+    return 0
+}
+
+check () {
+    if [ "$1" = "$2" ]; then
+        printf 'ok: %s\n' "$3"
+    else
+        printf 'FAIL: %s: got "%s" expected "%s"\n' "$3" "$1" "$2"
+        status=1
+    fi
+}
+
+a="a b"
+
+nargs $a
+check $n_args 2 'nargs $a'
+
+nargs "$a"
+check $n_args 1 'nargs "$a"'
+
+nargs "$a" $a
+check $n_args 3 'nargs "$a" $a'
+
+n_args=`nargs "$a"; echo $n_args`
+check $n_args 1 '`nargs "$a"`'
+
+n_args=`nargs "$a" $a; echo $n_args`
+check $n_args 3 '`nargs "$a" $a`'
+
+eval "nargs \"$a\""
+check $n_args 1 'eval "nargs \"$a\""'
+
+eval "nargs \"$a\" $a"
+check $n_args 3 'eval "nargs \"$a\" $a"'
+
+n_args=`eval "nargs \"$a\""; echo $n_args`
+check $n_args 1 'eval "nargs \"$a\""'
+
+n_args=`eval "nargs \"$a\" $a"; echo $n_args`
+check $n_args 3 'eval "nargs \"$a\" $a"'
+
+exit $status