Recognize MSYS compiler as MINGW compiler (#1290)

diff --git a/Makefile b/Makefile
index d8cb900..a77247d 100644
--- a/Makefile
+++ b/Makefile
@@ -302,7 +302,7 @@
 # On Windows we need the shared library to be executable
 else
 # mingw?
-IS_MINGW := $(shell $(CC) --version 2>/dev/null | grep -i mingw | wc -l)
+IS_MINGW := $(shell $(CC) --version 2>/dev/null | grep -i "\(mingw\|MSYS\)" | wc -l)
 ifeq ($(IS_MINGW),1)
 EXT = dll
 AR_EXT = lib