Remove extension from portable ilasm invocation

src/Test/Utilities/Portable/Metadata/IlasmUtilities.cs

@@ -31,7 +31,7 @@ private static string GetIlasmPath()
             }
             else
             {
-                return Path.Combine(AppContext.BaseDirectory, "ilasm.exe");
+                return Path.Combine(AppContext.BaseDirectory, "ilasm");
             }
         }
 
@@ -74,12 +74,12 @@ public static void IlasmTempAssembly(string declarations, bool appendDefaultHead
 
                 sourceFile.WriteAllText(completeIL);
 
-                var arguments = $"\"{sourceFile.Path}\" /DLL /out=\"{assemblyPath}\"";
+                var arguments = $"\"{sourceFile.Path}\" -DLL -out=\"{assemblyPath}\"";
 
                 if (includePdb && !MonoHelpers.IsRunningOnMono())
                 {
                     pdbPath = Path.ChangeExtension(assemblyPath, "pdb");
-                    arguments += string.Format(" /PDB=\"{0}\"", pdbPath);
+                    arguments += string.Format(" -PDB=\"{0}\"", pdbPath);
                 }
                 else
                 {