Update Buildroot, EDK2 and QEMU

[xiangmy]

As disscussed in https://github.com/OP-TEE/manifest/issues/179

• Buildroot fixed the glibc 2.33 compatibility issue (_STAT_VER was removed in glibc 2.33), we should upgrade the Buildroot to reflect that change.
• EDK2 fixed its incompatibility with python 3.9, so we should update it to edk2-stable202102
• QEMU fails to build with binutils 2.35 (https://bugs.launchpad.net/ubuntu/+source/binutils/+bug/1907789), hence, we need to update it to the latest version.

[jforissier]

• For commit "Update Buildroot": Please specify the version in the commit subject: "Update Buildroot to version 2021.02". With that: Acked-by: Jerome Forissier <jerome@forissier.org>
• For commit "Update EDK2": Please add prefix: "qemu_v8: update EDK2". With that: Acked-by: Jerome Forissier <jerome@forissier.org>
• For commit "Update QEMU": Please add prefix: "qemu, qemu_v8: update QEMU". With that: Acked-by: Jerome Forissier <jerome@forissier.org>

Mainline EDK2 is also used by fvp.xml, perhaps someone who can test it can try to upgrade?

[jforissier]

Small nit: no blank lines should be added between tags (Link:, Signed-off-by:, Acked-by: etc.).

[xiangmy]

Got you! Thanks for the reviewing!