title: How to set a CMake option() at command line
body: <p>I created a CMakeLists.txt that contains the following</p>
  
  <pre><code>project(P4V)
  cmake_minimum_required(VERSION 2.6)
  
  option(BUILD_STATIC_LIBS "Build the static library" ON)
  option(BUILD_SHARED_LIBS "Build the shared library" ON)
  option(BUILD_TESTS "Build test programs" OFF)
  
  include_directories(${CMAKE_SOURCE_DIR}/include)
  set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/lib)
  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/lib)
  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/bin)
  set(CMAKE_BUILD_TYPE Release)
  
  add_subdirectory(src)
  if(BUILD_TESTS)
      add_subdirectory(tests)
  endif(BUILD_TESTS)
  </code></pre>
  
  <p>By default BUILD_TESTS is OFF, how can I turn it ON without CMake GUI, but with cmake command itself?
  I tried the following, but it doesn't work</p>
  
  <pre><code>cmake .. -G %1 -DBUILD_SHARED_LIBS=ON -DBUILD_STATIC_LIBS=ON -DBUILD_TESTS=ON
  </code></pre>