Add /DLL switch when building shared libs with MSC

src/tools/msc.lua

@@ -154,6 +154,9 @@
 			_NoManifest = "/MANIFEST",
 			OmitDefaultLibrary = "/NODEFAULTLIB",
 			Symbols = "/DEBUG",
+		},
+		kind = {
+			SharedLib = "/DLL",
 		}
 	}
 

tests/tools/test_msc.lua

@@ -234,3 +234,9 @@
 		prepare()
 		test.contains("/MANIFEST:NO", msc.getldflags(cfg))
 	end
+
+	function suite.ldflags_onDLL()
+		kind "SharedLib"
+		prepare()
+		test.contains("/DLL", msc.getldflags(cfg))
+	end