message: build_system: more consistent compiler flags in root CMakeLists
diff: @@ -8,13 +8,16 @@ set(CMAKE_CXX_STANDARD 11)
  project(dronecore)
  -if(NOT MSVC)
  - # Clang and GCC
  - # We want C++11 and lots of warnings.
  +if(MSVC)
  + add_definitions(-DWINDOWS)
  + set(warnings "-WX -W2")
  +
  + # We need this so Windows links to e.g. dronecore_telemetry.dll.
  + # Without this option it will look for dronecore_telemetry.lib and fail.
  + option(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS "Export all symbols on Windows" ON)
  +else()
  # We are not using exceptions to make it easier to write wrappers.
  - add_definitions(
  - -fno-exceptions
  - )
  + add_definitions(-fno-exceptions)
  set(warnings "-Wall -Wextra -Werror -Wshadow -Wno-strict-aliasing -Wold-style-cast -Wdouble-promotion -Wformat=2")
  @@ -31,25 +34,10 @@ if(NOT MSVC)
  endif()
  set(warnings "${warnings} -Wuseless-cast -Wlogical-op")
  - endif()
  -else()
  - # MSBuild
  - add_definitions(
  - -DWINDOWS
  - )
  -
  - set(warnings "-WX -W2")
  -
  - # We need this so Windows links to e.g. dronecore_telemetry.dll.
  - # Without this option it will look for dronecore_telemetry.lib and fail.
  - option(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS "Export all symbols on Windows" ON)
  -endif()
  -
  -# Clang needs this warning disabled.
  -if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  - # Some time ago we needed `-stdlib=libc++` but that does not seem to be true anymore.
  + elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  set(warnings "${warnings} -Wno-missing-braces")
  endif()
  +endif()
  # We need a define if on APPLE
  if(APPLE)
  