From 67ae1d441dbc2d944a08b95178f99d2cf67169e1 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Mon, 28 Sep 2020 13:05:21 +0900
Subject: [PATCH] Do not use clang on cygwin

Its `__has_declspec_attribute()` is not reliable.  For instance,
while `__has_declspec_attribute(noalias)` is true but 'noalias'
attribute is warned as unknown.
---
 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index f7bbc36366..16e6457ce2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -101,7 +101,7 @@ AS_IF([test ! -z "$ac_cv_prog_CC" -a ! -z "$CC" -a "$CC" != "$ac_cv_prog_CC"], [
   AC_MSG_ERROR(cached CC is different -- throw away $cache_file
 (it is also a good idea to do 'make clean' before compiling))
 ])
-AS_CASE(["${build_os}"], [linux*], [
+AS_CASE(["${build_os}"], [linux*|cygwin*], [
     AC_CHECK_TOOLS([CC], [gcc clang cc])
 ], [
     # OpenBSD wants to prefer cc over gcc.