build.sh: Add support for x86_64 architecture in the Debian image build script.

Also introduces some QoL code changes, based on the output of ShellCheck

Bug: b:372169343
Change-Id: I35567a533442bfe9ce96a0f17ae40005e76ba684
diff --git a/build/debian/build_in_container.sh b/build/debian/build_in_container.sh
index 6bc366b..555ce90 100755
--- a/build/debian/build_in_container.sh
+++ b/build/debian/build_in_container.sh
@@ -1,5 +1,24 @@
 #!/bin/bash
 
-if [ -z $ANDROID_BUILD_TOP ]; then echo "forgot to source build/envsetup.sh?" && exit 1; fi
+if [ -z "$ANDROID_BUILD_TOP" ]; then echo "forgot to source build/envsetup.sh?" && exit 1; fi
 
-docker run --privileged -it -v $ANDROID_BUILD_TOP/packages/modules/Virtualization:/root/Virtualization -v /dev:/dev ubuntu:22.04 /root/Virtualization/build/debian/build.sh
+arch=aarch64
+while getopts "a:" option; do
+  case ${option} in
+    a)
+      if [[ "$OPTARG" != "aarch64" && "$OPTARG" != "x86_64" ]]; then
+        echo "Invalid architecture: $OPTARG"
+        exit
+      fi
+      arch="$OPTARG"
+      ;;
+    *)
+      echo "Invalid option: $OPTARG"
+      exit
+      ;;
+  esac
+done
+
+docker run --privileged -it -v \
+  "$ANDROID_BUILD_TOP/packages/modules/Virtualization:/root/Virtualization" -v \
+  /dev:/dev ubuntu:22.04 /root/Virtualization/build/debian/build.sh -a "$arch"