gh-117787: Autoconf: fix bashisms/semantic breakage of iOS checks (#117788)

Author: eli-schwartz

configure

@@ -6053,7 +6053,7 @@ if test "$PY_ENABLE_SHARED" = "1" && ( test -n "$ANDROID_API_LEVEL" || test "$MA
 fi
 
 # On iOS the shared libraries must be linked with the Python framework
-if test "$ac_sys_system" == "iOS"; then
+if test "$ac_sys_system" = "iOS"; then
   MODULE_DEPS_SHARED="$MODULE_DEPS_SHARED \$(PYTHONFRAMEWORKDIR)/\$(PYTHONFRAMEWORK)"
 fi