Limit coroutine implementations to Linux.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65865 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.ac

@@ -2327,13 +2327,13 @@ AS_IF([test "${universal_binary-no}" = yes ], [
 
 AC_MSG_CHECKING(native fiber implementation)
 AS_CASE(["$target_cpu-$target_os"],
-  [x*64-*], [
+  [x*64-*x], [
     AC_MSG_RESULT(amd64)
     COROUTINE_H=coroutine/amd64/Context.h
     AC_DEFINE_UNQUOTED(FIBER_USE_COROUTINE, ["$COROUTINE_H"])
     AC_LIBOBJ([coroutine/amd64/Context])
   ],
-  [*86-*], [
+  [*86-*x], [
     AC_MSG_RESULT(x86)
     COROUTINE_H=coroutine/x86/Context.h
     AC_DEFINE_UNQUOTED(FIBER_USE_COROUTINE, ["$COROUTINE_H"])