[Driver] Fix -static-libsan / -shared-libsan on Darwin

Don't ignore these flags on Darwin. The old behavior of using the
dynamic runtime when neither flag is passed is preserved.

llvm-svn: 315142
diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index 29fae00..78d7bf4 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -1049,7 +1049,8 @@
   if (Sanitize.needsUbsanRt())
     AddLinkSanitizerLibArgs(Args, CmdArgs,
                             Sanitize.requiresMinimalRuntime() ? "ubsan_minimal"
-                                                              : "ubsan");
+                                                              : "ubsan",
+                            Sanitize.needsSharedRt());
   if (Sanitize.needsTsanRt())
     AddLinkSanitizerLibArgs(Args, CmdArgs, "tsan");
   if (Sanitize.needsFuzzer() && !Args.hasArg(options::OPT_dynamiclib)) {