testing: probe gdb for supported architectures ahead of time

Currently when we encounter a gdb that is old or not built with
multiarch in mind we fail rather messily. Try and improve the
situation by probing ahead of time and setting
HOST_GDB_SUPPORTS_ARCH=y in the relevant tcg configs. We can then skip
and give a more meaningful message if we don't run the test.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230302190846.2593720-24-alex.bennee@linaro.org>
Message-Id: <20230303025805.625589-24-richard.henderson@linaro.org>

configure

@@ -230,6 +230,7 @@ stack_protector=""
 safe_stack=""
 use_containers="yes"
 gdb_bin=$(command -v "gdb-multiarch" || command -v "gdb")
+gdb_arches=""
 
 if test -e "$source_path/.git"
 then
@@ -2395,6 +2396,7 @@ if test -n "$gdb_bin"; then
     gdb_version=$($gdb_bin --version | head -n 1)
     if version_ge ${gdb_version##* } 9.1; then
         echo "HAVE_GDB_BIN=$gdb_bin" >> $config_host_mak
+        gdb_arches=$("$source_path/scripts/probe-gdb-support.py" $gdb_bin)
     else
         gdb_bin=""
     fi
@@ -2519,6 +2521,12 @@ for target in $target_list; do
       write_target_makefile "build-tcg-tests-$target" >> "$config_target_mak"
       echo "BUILD_STATIC=$build_static" >> "$config_target_mak"
       echo "QEMU=$PWD/$qemu" >> "$config_target_mak"
+
+      # will GDB work with these binaries?
+      if test "${gdb_arches#*$arch}" != "$gdb_arches"; then
+          echo "HOST_GDB_SUPPORTS_ARCH=y" >> "$config_target_mak"
+      fi
+
       echo "run-tcg-tests-$target: $qemu\$(EXESUF)" >> Makefile.prereqs
       tcg_tests_targets="$tcg_tests_targets $target"
   fi