[gdb/testsuite] Add untested for missing xml support in gdb.base/valgrind*.exp

Add untested in case missing xml support is detected in test-cases
gdb.base/valgrind*.exp.

Tested on x86_64-linux.

---
 gdb/testsuite/gdb.base/valgrind-bt.exp        | 1 +
 gdb/testsuite/gdb.base/valgrind-disp-step.exp | 1 +
 gdb/testsuite/gdb.base/valgrind-infcall-2.exp | 1 +
 gdb/testsuite/gdb.base/valgrind-infcall.exp   | 1 +
 4 files changed, 4 insertions(+)

diff --git a/gdb/testsuite/gdb.base/valgrind-bt.exp b/gdb/testsuite/gdb.base/valgrind-bt.exp
index 4b84a45d333..440c6e403e9 100644
--- a/gdb/testsuite/gdb.base/valgrind-bt.exp
+++ b/gdb/testsuite/gdb.base/valgrind-bt.exp
@@ -15,6 +15,7 @@
 
 if { [gdb_skip_xml_test] } {
     # Valgrind gdbserver requires gdb with xml support.
+    untested "missing xml support"
     return 0
 }
 
diff --git a/gdb/testsuite/gdb.base/valgrind-disp-step.exp b/gdb/testsuite/gdb.base/valgrind-disp-step.exp
index f9429fbd69a..88ac848ae2d 100644
--- a/gdb/testsuite/gdb.base/valgrind-disp-step.exp
+++ b/gdb/testsuite/gdb.base/valgrind-disp-step.exp
@@ -20,6 +20,7 @@
 
 if { [gdb_skip_xml_test] } {
     # Valgrind gdbserver requires gdb with xml support.
+    untested "missing xml support"
     return 0
 }
 
diff --git a/gdb/testsuite/gdb.base/valgrind-infcall-2.exp b/gdb/testsuite/gdb.base/valgrind-infcall-2.exp
index 30881ca72ea..a368717c1e8 100644
--- a/gdb/testsuite/gdb.base/valgrind-infcall-2.exp
+++ b/gdb/testsuite/gdb.base/valgrind-infcall-2.exp
@@ -31,6 +31,7 @@
 
 if { [gdb_skip_xml_test] } {
     # Valgrind gdbserver requires gdb with xml support.
+    untested "missing xml support"
     return 0
 }
 
diff --git a/gdb/testsuite/gdb.base/valgrind-infcall.exp b/gdb/testsuite/gdb.base/valgrind-infcall.exp
index 0108f92ceaf..9f49a320f52 100644
--- a/gdb/testsuite/gdb.base/valgrind-infcall.exp
+++ b/gdb/testsuite/gdb.base/valgrind-infcall.exp
@@ -15,6 +15,7 @@
 
 if { [gdb_skip_xml_test] } {
     # Valgrind gdbserver requires gdb with xml support.
+    untested "missing xml support"
     return 0
 }