Bug 521750 - Follow-up: add some actually used compilation options when detecting __thread support [r=bsmedberg]

configure.in

@@ -4160,12 +4160,16 @@ if test "$ac_cv_trouble_comparing_to_zero" = yes ; then
   AC_DEFINE(HAVE_CPP_TROUBLE_COMPARING_TO_ZERO)
 fi
 
+# try harder, when checking for __thread support, see bug 521750 comment #33 and below
+_SAVE_LDFLAGS=$LDFLAGS
+LDFLAGS="$LDFLAGS $DSO_PIC_CFLAGS $DSO_LDOPTS"
 AC_CACHE_CHECK(for __thread keyword for TLS variables,
                ac_cv_thread_keyword,
                [AC_TRY_LINK([__thread bool tlsIsMainThread = false;],
                             [return tlsIsMainThread;],
                             ac_cv_thread_keyword=yes,
                             ac_cv_thread_keyword=no)])
+LDFLAGS=$_SAVE_LDFLAGS
 if test "$ac_cv_thread_keyword" = yes; then
   AC_DEFINE(HAVE_THREAD_TLS_KEYWORD)
 fi