Update buildroot to 2018.08

Supports building with GCC 8.

Change-Id: I7b9b9e3b277de6d38be9373c042d85485a38f211
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/juno.xml b/juno.xml
index d41f371..5ef382d 100644
--- a/juno.xml
+++ b/juno.xml
@@ -19,7 +19,7 @@
 
         <!-- Misc gits -->
         <project path="arm-trusted-firmware" name="ARM-software/arm-trusted-firmware.git" revision="refs/tags/v1.5" clone-depth="1" />
-        <project path="buildroot"            name="buildroot/buildroot.git"               revision="62dca337fe72085d98b7603cfcff1279c48ba7d9" />
+        <project path="buildroot"            name="buildroot/buildroot.git"               revision="refs/tags/2018.08" clone-depth="1" />
         <project path="u-boot"               name="u-boot/u-boot.git"                     revision="refs/tags/v2018.03" clone-depth="1" />
         <project path="vexpress-firmware"    name="arm/vexpress-firmware.git"             revision="670a8336738046ac910f4ed3746edc1b4ecf086c" remote="linaro"/>
 </manifest>