refactor build script

1. remove unnecessary download in build.sh
2. set workdir in build_in_container.sh to get build artifacts

Bug: n/a
Test: build
Change-Id: Ic817d3e5d5d2c371113220f61a536f75267e713e
diff --git a/build/debian/build_in_container.sh b/build/debian/build_in_container.sh
index 555ce90..fd1a975 100755
--- a/build/debian/build_in_container.sh
+++ b/build/debian/build_in_container.sh
@@ -19,6 +19,6 @@
   esac
 done
 
-docker run --privileged -it -v \
+docker run --privileged -it --workdir /root/Virtualization/build/debian -v \
   "$ANDROID_BUILD_TOP/packages/modules/Virtualization:/root/Virtualization" -v \
   /dev:/dev ubuntu:22.04 /root/Virtualization/build/debian/build.sh -a "$arch"