BUILD: makefile: Fix building with closefrom() support enabled

I noticed the USE_CLOSEFROM define was not being passed along like the rest
during the build.

Looking around I see this was broken with the following two commits and related
series..

BUILD: Makefile: also report disabled options in the BUILD_OPTIONS variable
http://git.haproxy.org/?p=haproxy.git;a=commit;h=05fd82da76d1bbc8d65d63ab246bda7cbcf8481a

BUILD: pass all "USE_*" variables as -DUSE_* to the compiler
http://git.haproxy.org/?p=haproxy.git;a=commit;h=824cd00d3bda8f7f6d4c30baf77ba6c19ab47811

Looks like this should be back ported to 2.0, 2.1 and 2.2.
diff --git a/Makefile b/Makefile
index b18a731..b214db1 100644
--- a/Makefile
+++ b/Makefile
@@ -37,6 +37,7 @@
 #   USE_LUA              : enable Lua support.
 #   USE_FUTEX            : enable use of futex on kernel 2.6. Automatic.
 #   USE_ACCEPT4          : enable use of accept4() on linux. Automatic.
+#   USE_CLOSEFROM        : enable use of closefrom() on *bsd, solaris. Automatic.
 #   USE_PRCTL            : enable use of prctl(). Automatic.
 #   USE_ZLIB             : enable zlib library support.
 #   USE_SLZ              : enable slz library instead of zlib (pick at most one).
@@ -291,7 +292,7 @@
            USE_STATIC_PCRE USE_STATIC_PCRE2 USE_TPROXY USE_LINUX_TPROXY       \
            USE_LINUX_SPLICE USE_LIBCRYPT USE_CRYPT_H                          \
            USE_GETADDRINFO USE_OPENSSL USE_LUA USE_FUTEX USE_ACCEPT4          \
-           USE_ZLIB USE_SLZ USE_CPU_AFFINITY USE_TFO USE_NS                   \
+           USE_CLOSEFROM USE_ZLIB USE_SLZ USE_CPU_AFFINITY USE_TFO USE_NS     \
            USE_DL USE_RT USE_DEVICEATLAS USE_51DEGREES USE_WURFL USE_SYSTEMD  \
            USE_OBSOLETE_LINKER USE_PRCTL USE_THREAD_DUMP USE_EVPORTS