In e8b6b7ad, we relaxed the cmake version check down to 3.1, the first
version to expose target_compile_features().
However, an error while testing that change improperly concluded that
the change was OK. While target_compile_features() was indeed intriduced
in cmake 3.1, the actual feature we use it to test, cxx_std_11, was
really introduced only with cmake-3.8, which explained the actual
version that was requested before e8b6b7ad.
As Patrick noted, however, we can still convince cmake-3.1 to test
for C++11, by testing for an actual feature introduced in C++11, like
testing for cxx_range_for, which will instruct cmake to set the
appropriate C++11 options for the current compiler, which for gcc would
be adding -std=gnu++11.
Reported-by: Patrick Boettcher <patrick.boettcher@posteo.de>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
70f8af1fc9