[x265] Errors of compilation under Cygwin

[Steve Borho]

On 01/13, fangzhen wrote:
> Hi guys,
> 
> Recently, I compile x265-v1.8 under cygwin, and an error occurs:
> /usr/lib/gcc/i686-pc-cygwin/4.9.3/../../../../i686-pc-cygwin/bin/ld: unrecognized option '-znoexecstack'
> /usr/lib/gcc/i686-pc-cygwin/4.9.3/../../../../i686-pc-cygwin/bin/ld: use the --help option for usage information
> collect2: error: ld returned 1 exit status
> CMakeFiles/x265-shared.dir/build.make:223: recipe for target 'cygx265-68.dll' failed
> make[2]: *** [cygx265-68.dll] Error 1
> CMakeFiles/Makefile2:169: recipe for target 'CMakeFiles/x265-shared.dir/all' failed
> make[1]: *** [CMakeFiles/x265-shared.dir/all] Error 2
> Makefile:127: recipe for target 'all' failed
> make: *** [all] Error 2
>
> It seems there is an invalid option -znoexecstack. So I search the
> current directory, and find that two files contain this string
> '-znoexecstack':
>
> 
> And I remove the option -znoexecstack and try to make again and I succeed.
> From the two files, we can see that the option -znoexecstack is added for C++ compiler. So I want to make it clear why this option is added. What is wrong with my cmake?

1. cygwin is not a supported build env; if it mostly works that is
   accidental

2. -znoexecstack is required by many Linux distributions for security
   reasons, I believe.

-- 
Steve Borho