configure: Disable thread-safety warnings on macOS

The enablement of -Wthread-safety broke compilation on macOS (if
-Werror is enabled, like in our CI). Disable it there by default
until the problems are resolved.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20230301113425.286946-1-thuth@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/configure b/configure
index 50a0b80..219ff13 100755
--- a/configure
+++ b/configure
@@ -1230,7 +1230,10 @@
 add_to warn_flags -Wexpansion-to-defined
 add_to warn_flags -Wimplicit-fallthrough=2
 add_to warn_flags -Wmissing-format-attribute
-add_to warn_flags -Wthread-safety
+
+if test "$targetos" != "darwin"; then
+    add_to warn_flags -Wthread-safety
+fi
 
 nowarn_flags=
 add_to nowarn_flags -Wno-initializer-overrides