Automate assembler support for Win64 targets (more work is needed).

util/mk1mf.pl

diff --git a/util/mk1mf.pl b/util/mk1mf.pl
index d4cc3d9..cf29bf8 100755
--- a/util/mk1mf.pl
+++ b/util/mk1mf.pl
@@ -871,6 +871,7 @@
 			$ret.=&cc_compile_target("$to${o}$n$obj","${_}.c",$ex)
 			}
 		elsif (-f ($s="${d}${o}asm${o}${n}.pl") or
+		       ($s=~s/sha256/sha512/ and -f $s) or
 		       -f ($s="${d}${o}${n}.pl"))
 			{
 			$ret.=&perlasm_compile_target("$to${o}$n$obj",$s,$n);