[lit] Set shlibpath_var on OpenBSD

(cherry picked from commit 3eca0b3)

Author: brad0

clang/test/Unit/lit.cfg.py

@@ -45,7 +45,7 @@
         config.environment[var] = os.environ[var]
 
 def find_shlibpath_var():
-    if platform.system() in ['Linux', 'FreeBSD', 'NetBSD', 'SunOS']:
+    if platform.system() in ['Linux', 'FreeBSD', 'NetBSD', 'OpenBSD', 'SunOS']:
         yield 'LD_LIBRARY_PATH'
     elif platform.system() == 'Darwin':
         yield 'DYLD_LIBRARY_PATH'