[BUILD] fix MANDIR default location to match documentation
I found this while building for Fedora.
(cherry picked from commit a2b53f8831b84b7c8647d7e960b84defd3bcbfa8)
(cherry picked from commit 2cac232b966a252951073d7b1a4bba4c4a730978)
diff --git a/Makefile b/Makefile
index 1f940d3..dc39ec4 100644
--- a/Makefile
+++ b/Makefile
@@ -62,7 +62,7 @@
DESTDIR =
PREFIX = /usr/local
SBINDIR = $(PREFIX)/sbin
-MANDIR = $(PREFIX)/man
+MANDIR = $(PREFIX)/share/man
DOCDIR = $(PREFIX)/doc/haproxy
#### TARGET system