Bump buidlroot version to 2018.02.6

bsp/buildroot/package/gcc/6.4.0/940-uclinux-enable-threads.patch

@@ -0,0 +1,19 @@
+Enable POSIX threads for uClinux targets
+Reported upstream:
+https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71721
+
+Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
+
+diff -Nur gcc-6.1.0.orig/gcc/config.gcc gcc-6.1.0/gcc/config.gcc
+--- gcc-6.1.0.orig/gcc/config.gcc	2016-04-11 12:14:59.000000000 +0200
++++ gcc-6.1.0/gcc/config.gcc	2016-07-02 20:04:25.732169982 +0200
+@@ -833,6 +833,9 @@
+ *-*-uclinux*)
+   extra_options="$extra_options gnu-user.opt"
+   use_gcc_stdint=wrap
++  case ${enable_threads} in
++    "" | yes | posix) thread_file='posix' ;;
++  esac
+   tm_defines="$tm_defines DEFAULT_LIBC=LIBC_UCLIBC SINGLE_LIBC"
+   ;;
+ *-*-rdos*)