autoconf: Support cygwin in addition to mingw
diff --git a/configure.ac b/configure.ac
index 2d5b56a..ab4bcc3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -330,7 +330,7 @@
 	fi
 	abi="xcoff"
 	;;
-  *-*-mingw*)
+  *-*-mingw* | *-*-cygwin*)
 	abi="pecoff"
 	force_tls="0"
 	RPATH=""