Add support for qemuarm/64 machines with EFI

Fixes #667 (closed) Fixes docs#126 (closed)

TODO (do not merge if any pending):

• update docs
• mention new machines in build templates
• upstream edk2 and grub/grub-efi fixes - #766
• upstream the machines - #767 (closed)
• ci
• add ci jobs docs - #765
• drop unsupported machines from everywhere in this repo (qemuarm, qemuarm64, generic...)
• cleanup machine defconfigs - #770 (closed)

meta-oniro-staging/recipes-bsp/uefi/edk2-firmware_%.bbappend

+# SPDX-FileCopyrightText: Huawei Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+export GCC5_ARM_PREFIX = "${TARGET_PREFIX}"
+export CLANG38_ARM_PREFIX = "${TARGET_PREFIX}"
+
+do_install:prepend() {
+	# Some platforms use an ARCH suffix.
+	if [ ! -e "${B}/Build/${EDK2_PLATFORM}" ]; then
+		ln -s ${EDK2_PLATFORM}-${EDK2_ARCH} ${B}/Build/${EDK2_PLATFORM}
+	fi
+}