Fix make install targets

CMakeLists.txt

@@ -165,3 +165,9 @@ endif()
 if (NOT ${skip_unittests})
     add_subdirectory(tests)
 endif()
+
+if(WIN32)  
+else()  
+    install (TARGETS umqtt DESTINATION lib)  
+    install (FILES ${source_h_files} DESTINATION include/azureiot/azure_umqtt_c)  
+endif (WIN32)