Pass -dll to link.exe when building with -shared (PR22697)

And start building a test for non-clang-cl link.exe invocations.

llvm-svn: 231312
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 5d66605..a80214e 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -8098,7 +8098,9 @@
   if (Args.hasArg(options::OPT_g_Group))
     CmdArgs.push_back("-debug");
 
-  bool DLL = Args.hasArg(options::OPT__SLASH_LD, options::OPT__SLASH_LDd);
+  bool DLL = Args.hasArg(options::OPT__SLASH_LD,
+                         options::OPT__SLASH_LDd,
+                         options::OPT_shared);
   if (DLL) {
     CmdArgs.push_back(Args.MakeArgString("-dll"));