coreos/config: Workaround flaky checks in net-dns/bind-tools

The reasoning is written in the config file. But at the same time drop
the outdated stuff - there is no such flag like --without-ecdsa any
more.

coreos/config/env/net-dns/bind-tools

@@ -1,2 +1,9 @@
-# Work around failing OpenSSL feature detection.
-EXTRA_ECONF="--without-ecdsa"
+# Work around lame function attribute checks when cross-compiling.
+# Linker emits a bunch of irrelevant warnings and that trips configure
+# script up into thinking that those attributes are not
+# supported. Upstream bind-tools already fixed that by being smarter
+# and grepping for -Wattributes instead, but we are not yet packaging
+# it.
+
+EXTRA_ECONF+=" ax_cv_have_func_attribute_constructor=yes"
+EXTRA_ECONF+=" ax_cv_have_func_attribute_destructor=yes"