[pushed] [gdb/testsuite] Require allow_xml_test in gdb.base/foll-fork-syscall.exp

I build gdb without xml support, and ran into:
...
(gdb) catch syscall chdir
warning: Can not parse XML syscalls information; \
  XML support was disabled at compile time.
Unknown syscall name 'chdir'.^M
(gdb) FAIL: $exp: follow-fork-mode=parent: detach-on-fork=on: \
  test_catch_syscall: catch syscall chdir
...

Fix this by requiring allow_xml_test.
---
 gdb/testsuite/gdb.base/foll-fork-syscall.exp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/gdb/testsuite/gdb.base/foll-fork-syscall.exp b/gdb/testsuite/gdb.base/foll-fork-syscall.exp
index bbda7aba6e2..a283631f458 100644
--- a/gdb/testsuite/gdb.base/foll-fork-syscall.exp
+++ b/gdb/testsuite/gdb.base/foll-fork-syscall.exp
@@ -21,6 +21,7 @@
 require !gdb_debug_enabled
 require {is_any_target "i?86-*-*" "x86_64-*-*"}
 require allow_fork_tests
+require allow_xml_test
 
 standard_testfile
 

base-commit: f792df95877498ef71fe8f2849b1790e56baf4ab
-- 
2.51.0