Only link tests against -ldl on linux

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@220510 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/lit.cfg b/test/lit.cfg
index ff308b6..5e57cd6 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -431,7 +431,7 @@
         san = self.get_lit_conf('llvm_use_sanitizer', '').strip()
         if san:
             self.compile_flags += ['-fno-omit-frame-pointer']
-            if not sys.platform.startswith('freebsd'):
+            if sys.platform == 'linux2':
                 self.link_flags += ['-ldl']
             if san == 'Address':
                 self.compile_flags += ['-fsanitize=address']