fish doesn't build on RHEL 5

[zanchey]

Apparently I don't get emails when builds fail any more!

For some time now, the build has been failing on RHEL 5, as O_CLOEXEC is not available:

[   80s] g++ -O2 -g -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -D_LARGEFILE_SOURCE=1 -D_FILE_OFFSET_BITS=64 -fno-exceptions -Wall -Wno-sign-compare -D_GNU_SOURCE=1 -D_ISO99_SOURCE=1  -Ipcre2-10.21/src -iquote. -iquote./src/ -DLOCALEDIR=\"/usr/share/locale\" -DPREFIX=L\"/usr\" -DDATADIR=L\"/usr/share\" -DSYSCONFDIR=L\"/etc\" -DBINDIR=L\"/usr/bin\" -DDOCDIR=L\"/usr/share/doc/fish\"  -DFISH_BUILD_VERSION=\"2.2.0-787-g9aeed0d\" -c src/input_common.cpp -o obj/input_common.o
[   81s] src/env_universal_common.cpp: In member function 'bool env_universal_t::open_temporary_file(const wcstring&, wcstring*, int*)':
[   81s] src/env_universal_common.cpp:690: error: 'O_CLOEXEC' was not declared in this scope

RHEL5 isn't that old, so it would be good to continue supporting it.

[zanchey]

The problem here is that O_CLOEXEC is entirely the wrong flag to be passing - it should be FD_CLOEXEC!