printf: Ignore any options

This was misguidedly "fixed" in
9e08609f85, which made printf error out
with any "-"-prefixed words as the first argument.

Note: This means currently `printf --help` doesn't print the help.
This also matches `echo`, and we currently don't have anything to make
a literal `--help` execute a builtin help except for keywords. Oh well.

Fixes #9132

tests/checks/printf.fish

@@ -119,3 +119,18 @@ printf '%d\n' 0g
 # CHECKERR: 0g: value not completely converted (can't convert 'g')
 echo $status
 # CHECK: 1
+
+# Test that we ignore options
+printf -a
+printf --foo
+# CHECK: -a--foo
+echo
+
+set -l helpvar --help
+printf $helpvar
+echo
+# CHECK: --help
+
+printf --help
+echo
+# CHECK: --help