Bug 43916

On FreeBSD 8.x, we don't have O_CLOEXC and it cause build failure like:

x86_64-gentoo-freebsd8.2-gcc -c -I../../../../include
-I../../../../src/egl/main -I../../../../src/mapi -I../../../../src/gbm/main
-I../../../../src/gbm/backends/dri -DDEFAULT_DRIVER_DIR=\"/usr/lib64/dri\" 
-I/usr/include/libdrm   -DHAVE_X11_PLATFORM -D_THREAD_SAFE   -w -O2
-march=nocona -mtune=nocona -pipe -fno-ivopts -ffast-math -Wall
-Wmissing-prototypes -std=c99 -ffast-math -fno-strict-aliasing  -fPIC 
-DUSE_X86_64_ASM -DTEXTURE_FLOAT_ENABLED -DHAVE_POSIX_MEMALIGN -DUSE_XCB
-DPTHREADS -DUSE_EXTERNAL_DXTN_LIB=1 -DIN_DRI_DRIVER -DHAVE_ALIAS
-DGLX_INDIRECT_RENDERING -DGLX_DIRECT_RENDERING -DHAVE_XCB_DRI2
-DXCB_DRI2_CONNECT_DEVICE_NAME_BROKEN -fvisibility=hidden
-D_EGL_MAIN=_eglBuiltInDriverDRI2 -DHAVE_SHARED_GLAPI platform_x11.c -o
platform_x11.o
platform_x11.c: In function 'dri2_initialize_x11_dri2':
platform_x11.c:1000: error: 'O_CLOEXEC' undeclared (first use in this function)
platform_x11.c:1000: error: (Each undeclared identifier is reported only once
platform_x11.c:1000: error: for each function it appears in.)
gmake[4]: *** [platform_x11.o] Error 1
gmake[4]: *** Waiting for unfinished jobs....
gmake[4]: Leaving directory
`/var/tmp/portage/media-libs/mesa-7.11/work/Mesa-7.11/src/egl/drivers/dri2'
gmake[3]: *** [subdirs] Error 1
gmake[3]: Leaving directory
`/var/tmp/portage/media-libs/mesa-7.11/work/Mesa-7.11/src/egl/drivers'
gmake[2]: *** [subdirs] Error 1
gmake[2]: Leaving directory
`/var/tmp/portage/media-libs/mesa-7.11/work/Mesa-7.11/src/egl'
gmake[1]: *** [subdirs] Error 1
gmake[1]: Leaving directory
`/var/tmp/portage/media-libs/mesa-7.11/work/Mesa-7.11/src'
gmake: *** [default] Error 1