Re-allow auto-detect rather than do =ON to ensure the toolchain supports it.
https://bugs.gentoo.org/754021
https://github.com/qt/qtbase/commit/48675dfa3 (revert of)
--- a/configure.cmake
+++ b/configure.cmake
@@ -784,3 +784,2 @@
     CONDITION NOT WIN32 AND TEST_no_direct_extern_access
-    AUTODETECT OFF
 )