[gdb/testsuite] Require use_gdb_stub == 0 where appropriate

When running with target board native-gdbserver, we run into a number of FAILs
due to use of the start command (and similar), which is not supported when
use_gdb_stub == 1.

Fix this by:
- requiring use_gdb_stub == 0 for the entire test-case, or
- guarding some tests in the test-case with use_gdb_stub == 0.

Tested on x86_64-linux.

gdb/testsuite/gdb.dwarf2/frame-inlined-in-outer-frame.exp

@@ -25,6 +25,9 @@
 # Because of (1), the test has to be written in assembly with explicit CFI
 # directives.
 
+# Check if starti command is supported.
+require use_gdb_stub 0
+
 load_lib dwarf.exp
 
 if {![dwarf2_support]} {

gdb/testsuite/gdb.mi/mi-async.exp

@@ -25,6 +25,9 @@ if { !([isnative] && [istarget *-linux*]) } then {
   return
 }
 
+# Check if start command is supported.
+require use_gdb_stub 0
+
 # The plan is for async mode to become the default but toggle for now.
 set saved_gdbflags $GDBFLAGS
 set GDBFLAGS [concat $GDBFLAGS " -ex \"set mi-async on\""]

gdb/testsuite/gdb.python/python.exp

@@ -539,6 +539,8 @@ gdb_test "print \$cvar3" "= void" \
 # "show commands".
 gdb_test "python gdb.execute(\"show commands\")" "$decimal  print \\\$cvar3.*"
 
+# Check if starti command is supported.
+if { [use_gdb_stub] == 0 } {
     # Test that the from_tty argument to gdb.execute is effective. If
     # False, the user is not prompted for decisions such as restarting the
     # program, and "yes" is assumed. If True, the user is prompted.
@@ -558,3 +560,4 @@ gdb_test_multiple "python gdb.execute('starti', from_tty=True)" $test {
 	    gdb_test "y" "Starting program:.*" $gdb_test_name
 	}
     }
+}

gdb/testsuite/gdb.reverse/insn-reverse.exp

@@ -17,6 +17,9 @@ if ![supports_reverse] {
     return
 }
 
+# Check if start command is supported.
+require use_gdb_stub 0
+
 standard_testfile
 
 if {[prepare_for_testing "failed to prepare" $testfile $srcfile \

gdb/testsuite/gdb.tui/tui-missing-src.exp

@@ -25,6 +25,9 @@
 #    layout must show the contents of f2.c.
 # 7. Going back to main() shall result in no contents again.
 
+# Check if start command is supported.
+require use_gdb_stub 0
+
 tuiterm_env
 
 standard_testfile

gdb/testsuite/lib/gdb.exp

@@ -8251,6 +8251,9 @@ proc require { fn arg1 {arg2 ""} } {
 	"ensure_gdb_index $binfile -dwarf-5 != -1" {
 	    set msg "Couldn't ensure index in binfile"
 	}
+	"use_gdb_stub == 0" {
+	    set msg "Remote stub used"
+	}
 	default { set msg "$fn != $val" }
     }