cmake 4.0.0 fails to build with cygwin 3.7.0-0.19

[Jeremy Drake]

I tried to build cmake 4.0.0 with latest test gcc and cygwin packages, and
got the following error

/home/WDAGUtilityAccount/cmake-4.0.0/Utilities/cmcurl/lib/rand.c: In
function ‘weak_random’:
/home/WDAGUtilityAccount/cmake-4.0.0/Utilities/cmcurl/lib/rand.c:124:21:
error: implicit declaration of function ‘arc4random’; did you mean
‘srandom’? [-Wimplicit-function-declaration]
  124 |   r = (unsigned int)arc4random();
      |                     ^~~~~~~~~~
      |                     srandom
make[2]: *** [Utilities/cmcurl/lib/CMakeFiles/cmcurl.dir/build.make:1423:
Utilities/cmcurl/lib/CMakeFiles/cmcurl.dir/rand.c.o] Error 1
make[2]: *** Waiting for unfinished jobs....


CYGWIN_NT-10.0-22621 f6904e59-bb48-4060-bea5-cf49a76e528e
3.7.0-0.19.g6c5537c0298e.x86_64 2025-03-28 19:43 UTC x86_64 Cygwin

gcc version 15.0.1 20250223 (experimental) (GCC)

This was trying to investigate
https://github.com/msys2/msys2-runtime/issues/272