Manually install rustup when building debian VM

Unlike Debian, Ubuntu doesn't have rustup package in apt repository. So
it requires to execute command bringing files from official site.

And added missing dep to build rust pkg

Bug: 340126051
Test: sudo ./build.sh
Test: ./build_in_container.sh
Change-Id: I5775fb24086864f3835d894285aa8d9f2642ce60
diff --git a/build/debian/build.sh b/build/debian/build.sh
index eff59a0..5894eaf 100755
--- a/build/debian/build.sh
+++ b/build/debian/build.sh
@@ -38,13 +38,16 @@
 	DEBIAN_FRONTEND=noninteractive \
 	apt install --no-install-recommends --assume-yes \
 		binfmt-support \
+		build-essential \
 		ca-certificates \
+		curl \
 		debsums \
 		dosfstools \
 		fai-server \
 		fai-setup-storage \
 		fdisk \
 		gcc-aarch64-linux-gnu \
+		libc6-dev-arm64-cross \
 		make \
 		python3 \
 		python3-libcloud \
@@ -57,11 +60,12 @@
 		udev \
 
 
-	which cargo > /dev/null 2>&1 || {
-		apt install --no-install-recommends --assume-yes rustup
-		rustup default stable
-		rustup update
-	}
+	if [ ! -f $HOME/.cargo/bin/cargo ]; then
+		curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+	fi
+
+        source $HOME/.cargo/env
+        rustup target add aarch64-unknown-linux-gnu
 
         sed -i s/losetup\ -f/losetup\ -P\ -f/g /usr/sbin/fai-diskimage
         sed -i 's/wget \$/wget -t 0 \$/g' /usr/share/debootstrap/functions
@@ -96,7 +100,7 @@
 	wget ${url} -O ${dst}/files/usr/local/bin/ttyd/AVF
 	chmod 777 ${dst}/files/usr/local/bin/ttyd/AVF
 
-	pushd forwarder_guest > /dev/null
+        pushd $(dirname $0)/forwarder_guest > /dev/null
 		RUSTFLAGS="-C linker=aarch64-linux-gnu-gcc" cargo build \
 			--target aarch64-unknown-linux-gnu \
 			--target-dir ${workdir}/forwarder_guest