update tested platforms in README

README.md

@@ -9,9 +9,16 @@ Inspired by [parrotsay](https://github.com/matheuss/parrotsay).
 
 ## Building.
 
-This has been tested only with gcc 6.3.0 and TinyCC 0.9.27 in Debian Stretch.
+This has been tested only with:
+
+* gcc 6.3.0 in Debian Stretch
+* TinyCC 0.9.27 in Debian Stretch
+* clang 6.0.0 on FreeBSD 11.2-RELEASE (with warnings)
 
 To build just do
 
     gcc parrotsay.c -o parrotsay
-    
+
+Or
+
+    clang parrotsay.c -o parrotsay