docs: Add a guide for testing on AArch64

The support of AArch64 is in very early stage. The steps in building and
runing on X86 and AArch64 can not align well yet. Adding AArch64 content
to README.md would produce much divergence.
Adding a guide in docs/ folder could be a better way to start now.

Signed-off-by: Michael Zhao <michael.zhao@arm.com>

scripts/dev_cli.sh

@@ -208,6 +208,11 @@ cmd_build() {
         rustflags="-C link-arg=-lgcc"
     fi
 
+    # A workaround on Arm64 to avoid build errors in kvm-bindings
+    if [ $(uname -m) = "aarch64" ]; then
+        sed -i 's/"with-serde",\ //g' "$CLH_ROOT_DIR"/vmm/Cargo.toml
+    fi
+
     $DOCKER_RUNTIME run \
 	   --user "$(id -u):$(id -g)" \
 	   --workdir "$CTR_CLH_ROOT_DIR" \