MINGW: set rb_cv_msvcrt=ucrt and RT_VER=140 when UCRT is used

configure.ac

@@ -450,11 +450,13 @@ AS_CASE(["$target_os"],
 		    [[FILE* volatile f = stdin; return 0;]])],
 		    [rb_cv_msvcrt=`$OBJDUMP -p conftest$ac_exeext |
 				   tr A-Z a-z |
-				   sed -n '/^[[ 	]]*dll name: \(msvc.*\)\.dll$/{s//\1/p;q;}'`],
+				   sed -n '/^[[ 	]]*dll name: \(msvc.*\)\.dll$/{s//\1/p;q;};
+					/^[[ 	]]*dll name: \(ucrtbase\|api-ms-win-crt-.*\)\.dll$/{s//ucrt/p;q;}'`],
 		    [rb_cv_msvcrt=msvcrt])
 	test "$rb_cv_msvcrt" = "" && rb_cv_msvcrt=msvcrt])
 	RT_VER=`echo "$rb_cv_msvcrt" | tr -cd [0-9]`
 	test "$RT_VER" = "" && RT_VER=60
+	test "$rb_cv_msvcrt" = "ucrt" && RT_VER=140
 	AC_DEFINE_UNQUOTED(RUBY_MSVCRT_VERSION, $RT_VER)
 	sysconfdir=
     ])