[gdb/testsuite] Fix gdb.base/list-no-debug.exp on debian

On debian 12, aarch64-linux I run into:
...
(gdb) list .^M
No symbol table is loaded.  Use the "file" command.^M
(gdb) FAIL: gdb.base/list-nodebug.exp: first 'list .'
...

The test-case expects some debug info, but none for main.  Instead, there's no
debug info at all.

Fix this by adding another source file to the test-case, and compiling it with
debug info.

Tested on aarch64-linux.

Approved-By: Andrew Burgess <aburgess@redhat.com>

PR testsuite/31290
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31290

gdb/testsuite/gdb.base/list-nodebug-2.c

@@ -0,0 +1,24 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2024 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+extern int foo (void);
+
+int
+foo (void)
+{
+  return 0;
+}

gdb/testsuite/gdb.base/list-nodebug.c

@@ -15,7 +15,10 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
-int main ()
+extern int foo (void);
+
+int
+main (void)
 {
-    return 0;
+  return foo ();
 }

gdb/testsuite/gdb.base/list-nodebug.exp

@@ -16,10 +16,13 @@
 # Test that using the command "list" in a file with no debug information
 # will not crash GDB and will give reasonable output.
 
-standard_testfile .c
+standard_testfile .c -2.c
 
-if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
-    {nodebug}]} {
+if { [prepare_for_testing_full "failed to prepare" \
+	  [list \
+	       $testfile {} \
+	       $srcfile {nodebug} \
+	       $srcfile2 {debug}]] } {
     return -1
 }