build: align minimum build dependencies with ndn-cxx

 * boost 1.65.1
 * gcc 7.4
 * clang 6.0
 * Xcode 10.0 (11.3 or later recommended)

Change-Id: I5e41f2a70d6c510dcb889a083a51504121b4627d
diff --git a/docs/INSTALL.rst b/docs/INSTALL.rst
index 231d8ae..a73b211 100644
--- a/docs/INSTALL.rst
+++ b/docs/INSTALL.rst
@@ -22,6 +22,7 @@
 -  Fedora >= 29
 -  Gentoo Linux
 -  Raspberry Pi OS (formerly Raspbian) >= 2019-06-20
+-  FreeBSD >= 12.0
 -  macOS 10.14
 
 .. _Install NFD on Ubuntu Linux using the NDN PPA repository: