detect OpenBSD

Index: src/taglib.nim
--- src/taglib.nim.orig
+++ src/taglib.nim
@@ -1,13 +1,14 @@
 import times, os, filetype, strformat, json
 import impl, utils
 
-when not defined(linux):
+when not defined(linux) and not defined(openbsd):
   proc findExistant(s: varargs[string]): string =
     result = s[0]
     for x in s:
       if dirExists x: return x
   const taglibPath = findExistant("C:/taglib", "D:/taglib", "C:/Libraries/taglib", "D:/Libraries/taglib")
 
+const taglibPath {.strdefine.} = "/usr/local"
 const taglibInclude {.strdefine.} =
   when defined(flatpak): "/app/include/taglib"
   elif defined(linux): "/usr/include/taglib"
