message: android(toolchain): detailed error message
diff: @@ -810,7 +810,7 @@ unset(__real_api_level)
  # validate
  list( FIND ANDROID_SUPPORTED_NATIVE_API_LEVELS "${ANDROID_NATIVE_API_LEVEL}" __levelIdx )
  if( __levelIdx EQUAL -1 )
  - message( SEND_ERROR "Specified Android native API level 'android-${ANDROID_NATIVE_API_LEVEL}' is not supported by your NDK/toolchain." )
  + message( SEND_ERROR "Specified Android native API level 'android-${ANDROID_NATIVE_API_LEVEL}' is not supported by your NDK/toolchain.\nSupported values of ANDROID_NATIVE_API_LEVEL: ${ANDROID_SUPPORTED_NATIVE_API_LEVELS}" )
  else()
  if( BUILD_WITH_ANDROID_NDK )
  __DETECT_NATIVE_API_LEVEL( __realApiLevel "${ANDROID_NDK}/platforms/android-${ANDROID_NATIVE_API_LEVEL}/arch-${ANDROID_ARCH_NAME}/usr/include/android/api-level.h" )
  