Try to suppress warning on some CI

http://ci.rvm.jp/results/trunk-asserts-nopara@silicon-docker/1149270
```
/home/ko1/ruby/src/trunk-asserts-nopara/process.c: In function 'assert_close_on_exec':
/home/ko1/ruby/src/trunk-asserts-nopara/process.c:298:9: warning: ignoring return value of 'write', declared with attribute warn_unused_result [-Wunused-result]
         (void)write(2, m, sizeof(m) - 1);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

workaround from https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425#c34

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64029 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/process.c b/process.c
index f0d1b87434..d1d33dd1b0 100644
--- a/process.c
+++ b/process.c
@@ -295,7 +295,7 @@ assert_close_on_exec(int fd)
     int flags = fcntl(fd, F_GETFD);
     if (flags == -1) {
         static const char m[] = "reserved FD closed unexpectedly?\n";
-        (void)write(2, m, sizeof(m) - 1);
+        (void)!write(2, m, sizeof(m) - 1);
         return;
     }
     if (flags & FD_CLOEXEC) return;