libuv: linux/sparc64: use fcntl to set and clear O_NONBLOCK

Upstream libuv commits:

* node-v0.6.0~28 (linux: use ioctl(FIONBIO) to set O_NONBLOCK, saves a syscall, 2011-10-29)
* v1.11.0~11 (unix: use async-signal safe functions between fork and exec, 2016-12-12)

left an asymmetry in the way O_NONBLOCK is set and cleared.  Normally
ioctl/FIONBIO is used for both.  However, uv_spawn uses fcntl/O_NONBLOCK
to clear O_NONBLOCK between fork and exec.  This fails on Linux/sparc64
where setting via ioctl/FIONBIO actually sets two bits (in O_NDELAY)
that cause clearing via fcntl/O_NONBLOCK to be silently ignored (though
clearing via ioctl/FIONBIO or fcntl/O_NDELAY works).

Since CMake commit v3.11.0-rc1~117^2 (CTest: Re-implement test process
handling using libuv, 2017-12-10), CTest uses libuv.  On Linux/sparc64
child processes have been started with non-blocking output pipes.  This
can lead to write errors or lost output from children not prepared to
deal with `EAGAIN` on stdout or stderr.

Fix this for now by switching libuv back to fcntl/O_NONBLOCK to set and
clear O_NONBLOCK when compiled on Linux/sparc64.

LibUV-Issue: 1830
Fixes: #17941

Utilities/cmlibuv/src/unix/internal.h

@@ -184,7 +184,7 @@ struct uv__stream_queued_fds_s {
     defined(__DragonFly__) || \
     defined(__FreeBSD__) || \
     defined(__FreeBSD_kernel__) || \
-    defined(__linux__) || \
+    (defined(__linux__) && !defined(__sparc__)) || \
     defined(__OpenBSD__) || \
     defined(__NetBSD__)
 #define uv__cloexec uv__cloexec_ioctl