Bump buidlroot version to 2018.02.6

bsp/buildroot/package/zsh/Config.in

@@ -4,9 +4,9 @@ config BR2_PACKAGE_ZSH
 	depends on BR2_PACKAGE_BUSYBOX_SHOW_OTHERS
 	select BR2_PACKAGE_NCURSES
 	help
-	  zsh is a shell designed for interactive use, although it is also
-	  a powerful scripting language. Many of the useful features of bash,
-	  ksh, and tcsh were incorporated into zsh; many original features
-	  were added.
+	  zsh is a shell designed for interactive use, although it is
+	  also a powerful scripting language. Many of the useful
+	  features of bash, ksh, and tcsh were incorporated into zsh;
+	  many original features were added.
 
 	  http://www.zsh.org/

bsp/buildroot/package/zsh/zsh.hash

@@ -1,4 +1,7 @@
 # From http://www.zsh.org/pub/MD5SUM
-md5	c5ba34e68fcf62a2e78adc56bf3d328a	zsh-5.3.tar.xz
-# Calculated based on the hash above
-sha256	76f82cfd5ce373cf799a03b6f395283f128430db49202e3e3f512fb5a19d6f8a	zsh-5.3.tar.xz
+md5	dfe156fd69b0d8d1745ecf6d6e02e047	zsh-5.4.2.tar.gz
+# Calculated based on the hash above and after checking signature
+# http://www.zsh.org/pub/zsh-5.4.2.tar.gz.asc
+sha256	957bcdb2c57f64c02f673693ea5a7518ef24b6557aeb3a4ce222cefa6d74acc9	zsh-5.4.2.tar.gz
+# Locally calculated
+sha256	d06fdf3ef9b1ec69d6b9e170b0a9516fbad3523261ff1668bde3bfea6e0ef5f5  LICENCE

bsp/buildroot/package/zsh/zsh.mk

@@ -4,11 +4,11 @@
 #
 ################################################################################
 
-ZSH_VERSION = 5.3
+ZSH_VERSION = 5.4.2
 ZSH_SITE = http://www.zsh.org/pub
-ZSH_SOURCE = zsh-$(ZSH_VERSION).tar.xz
 ZSH_DEPENDENCIES = ncurses
 ZSH_CONF_OPTS = --bindir=/bin
+ZSH_CONF_ENV = zsh_cv_sys_nis=no zsh_cv_sys_nis_plus=no
 ZSH_LICENSE = MIT-like
 ZSH_LICENSE_FILES = LICENCE