Avoid warning from mingw for shared library
diff --git a/library/Makefile b/library/Makefile
index 44a725c..f2e553f 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -19,8 +19,11 @@
 
 # To compile as a shared library:
 ifdef SHARED
+# all code is position-indep with mingw, avoid warning about useless flag
+ifndef WINDOWS
 CFLAGS += -fPIC
 endif
+endif
 
 SOVERSION=8