Update Buildroot to version 2021.02

As Buildroot fixed [1] the glibc 2.33 compatibility issue, we should update
the Buildroot to reflect that change.

Link: [1] https://git.busybox.net/buildroot/commit/?id=f45925a951318e9e53bead80b363e004301adc6f
Signed-off-by: Mingyuan Xiang <xiang_my@outlook.com>
Acked-by: Jerome Forissier <jerome@forissier.org>
diff --git a/qemu_v8.xml b/qemu_v8.xml
index 219ec3b..806ddf0 100644
--- a/qemu_v8.xml
+++ b/qemu_v8.xml
@@ -20,7 +20,7 @@
         <project path="soc_term"             name="linaro-swg/soc_term.git" />
 
         <!-- Misc gits -->
-        <project path="buildroot"            name="buildroot/buildroot.git"               revision="refs/tags/2020.08" clone-depth="1" />
+        <project path="buildroot"            name="buildroot/buildroot.git"               revision="refs/tags/2021.02" clone-depth="1" />
         <project path="edk2"                 name="tianocore/edk2.git"                    revision="refs/tags/edk2-stable201905" sync-s="true" />
         <project path="mbedtls"              name="ARMmbed/mbedtls.git"                   revision="refs/tags/mbedtls-2.16.0" clone-depth="1" />
         <project path="qemu"                 name="qemu/qemu.git"                         revision="refs/tags/v5.1.0" clone-depth="1" />