[pushed] Don't run gdb.gdb/ selftests if use_gdb_stub is true

[Pedro Alves <palves at redhat dot com>]

If we make the native-gdbserver board be !is_remote, then the few
tests that use the selftest-support.exp routines to debug gdb itself
start running, and fail, with something like:

  Running ..../src/gdb/testsuite/gdb.gdb/selftest.exp ...
  ERROR: tcl error sourcing ..../src/gdb/testsuite/gdb.gdb/selftest.exp.
  ERROR: gdbserver does not support run [....] without extended-remote
      while executing
  "error "gdbserver does not support $command without extended-remote""
      (procedure "gdb_test_multiple" line 25)
      invoked from within
  "gdb_test_multiple "run $INTERNAL_GDBFLAGS" "$description" {
	  -re "Starting program.*Breakpoint \[0-9\]+,.*$function \\(\\).* at .*main.c:.*$gdb..."
      (procedure "selftest_setup" line 45)

This commit makes sure those tests continue to be skipped.

gdb/testsuite/ChangeLog:
2017-10-13  Pedro Alves  <palves@redhat.com>

	* lib/selftest-support.exp (selftest_setup): Extend comments, and
	also skip on stub-like targets.
---
 gdb/testsuite/ChangeLog                |  5 +++++
 gdb/testsuite/lib/selftest-support.exp | 19 +++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 2e7eb1d..aa016c8 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2017-10-13  Pedro Alves  <palves@redhat.com>
 
+	* lib/selftest-support.exp (selftest_setup): Extend comments, and
+	also skip on stub-like targets.
+
+2017-10-13  Pedro Alves  <palves@redhat.com>
+
 	PR gdb/22293
 	* gdb.base/find-unmapped.exp: Don't skip if is_remote target.
 	(top level): Move some tests to ...
diff --git a/gdb/testsuite/lib/selftest-support.exp b/gdb/testsuite/lib/selftest-support.exp
index 987b5c8..798d19d 100644
--- a/gdb/testsuite/lib/selftest-support.exp
+++ b/gdb/testsuite/lib/selftest-support.exp
@@ -124,8 +124,23 @@ proc selftest_setup { executable function } {
 proc do_self_tests {function body} {
     global GDB tool
 
-    # Are we on a target board.
-    if { [is_remote target] || ![isnative] } then {
+    # Are we testing with a remote board?  In that case, the target
+    # won't have access to the GDB's auxilliary data files
+    # (data-directory, etc.).  It's simpler to just skip.
+    if [is_remote target] {
+	return
+    }
+
+    # ... or seemingly testing with a cross debugger?  Likely GDB
+    # wouldn't be able to debug itself then...
+    if ![isnative] {
+	return
+    }
+
+    # ... or with a stub-like server?  I.e., gdbserver + "target
+    # remote"?  In that case we won't be able to pass command line
+    # arguments to GDB, and selftest_setup wants to do exactly that.
+    if [target_info exists use_gdb_stub] {
 	return
     }
 
-- 
2.5.5