CMake: Use CMAKE_CXX_STANDARD instead of passing -std=c++14

[ligfx]

Available since CMake 3.1

[lioncash]

set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

will likely be preferable to have set as well.

[ligfx]

set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

will likely be preferable to have set as well.

Sure, I'll add those in and see what happens.

[ligfx]

The Android build seems to be running into android/ndk#222, where something in the NDK's toolchain file prevents CMAKE_CXX_STANDARD from working.

[Orphis]

Yes, and I knew of the issue, which is why I didn't use the flag.

[Orphis]

On a side note, the Android support in 3.7 (independent from Google's Gradle integration) works fine with it. Not sure we want to use it though...

[ligfx]

@Orphis: there are two proposed fixes up for AOSP (https://android-review.googlesource.com/#/c/326383/ (mine) and https://android-review.googlesource.com/#/c/324419/). Hopefully something will get merged for r14, and then CMAKE_CXX_STANDARD will work as intended.

In the meantime... what do you think about something like

# The Android NDK toolchain file is broken.
# See https://github.com/android-ndk/ndk/issues/222
if(CMAKE_TOOLCHAIN_FILE MATCHES "android.toolchain.cmake$")
  set(_new_toolchain_file "${CMAKE_CURRENT_BINARY_DIR}/android.toolchain.cmake")
  if(NOT EXISTS "${_new_toolchain_file}")
    file(TO_CMAKE_PATH "${CMAKE_TOOLCHAIN_FILE}" CMAKE_TOOLCHAIN_FILE)
    file(WRITE "${_new_toolchain_file}" "
      include(\"${CMAKE_TOOLCHAIN_FILE}\")
      set(CMAKE_C_COMPILER_ID_RUN FALSE)
      set(CMAKE_CXX_COMPILER_ID_RUN FALSE)
    ")
    set(CMAKE_TOOLCHAIN_FILE "${_new_toolchain_file}")
  endif()
endif()

? Too much?

[Orphis]

Something will be merged for r14, the issue is tagged with r14 in Github after all.
Yours look much better and I wonder why CMake would have issues detecting the compiler at all.

[degasus]

The android buildbot was updated a few weeks ago, may you rebase and ask anyone to merge it? LGTM.