fix: build native JNI lib on aarch64 CI runners

The multiArch=false path skips architectures whose name doesn't match
the host arch, but ARCHITECTURES uses Maven's classifier spelling
'aarch_64' while `arch` reports 'aarch64'. On the ARM runner this
mismatch caused every arch to be skipped, so no .so was built and the
unit tests crashed loading the native library.

Normalize the host arch to 'aarch_64' before comparing.

Author: maxday

aws-lambda-java-runtime-interface-client/src/main/jni/build-jni-lib.sh

@@ -118,10 +118,17 @@ else
   declare -a ARCHITECTURES=("x86_64" "aarch_64")
   declare -a LIBC_IMPLS=("glibc" "musl")
 
+  # `arch` reports the host as `aarch64`, but we use Maven's classifier
+  # spelling `aarch_64` in ARCHITECTURES, so normalize before comparing.
+  host_arch=$(arch)
+  if [ "${host_arch}" == "aarch64" ]; then
+      host_arch="aarch_64"
+  fi
+
   for arch in "${ARCHITECTURES[@]}"; do
 
-      if [[ "${MULTI_ARCH}" != "true" ]] && [[ "$(arch)" != "${arch}" ]]; then
-          echo "multi arch build not requested and host arch is $(arch), so skipping ${arch}..."
+      if [[ "${MULTI_ARCH}" != "true" ]] && [[ "${host_arch}" != "${arch}" ]]; then
+          echo "multi arch build not requested and host arch is ${host_arch}, so skipping ${arch}..."
           continue
       fi