ruby: disable fiddle support for bfin

Disable fiddle support because of compile failure (no ffi_closure support
for bfin).

Fixes:
 http://autobuild.buildroot.net/results/0a8/0a854274b520d4daca3911a64777a447b5756a52/

[Thomas: slightly adjust the comment wording.]

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/ruby/ruby.mk

@@ -30,6 +30,9 @@ RUBY_CONF_ENV = CFLAGS="$(RUBY_CFLAGS)"
 
 ifeq ($(BR2_bfin),y)
 RUBY_CONF_ENV = ac_cv_func_dl_iterate_phdr=no
+# Blackfin doesn't have FFI closure support, needed by the fiddle
+# extension.
+RUBY_CONF_OPTS += --with-out-ext=fiddle
 endif
 
 # Force optionals to build before we do