Fix compilation with MinGW32

Signed-off-by: Cameron Cawley <ccawley2011@gmail.com>
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index 7481c5b..a620178 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -44,9 +44,12 @@
 
 #include <string.h>
 
+#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__)) || defined(__MINGW32__)
+#include <strings.h>
+#endif
+
 #if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
 #include <unistd.h>
-#include <strings.h>
 #endif
 
 /* Type for Hex parameters */