Install squashfs-tools, wget, and curl in chroot for initramfs hooks

The initramfs hooks copy binaries from the chroot environment, so these tools
must be installed there. Without squashfs-tools, unsquashfs is missing from the
initramfs and the netboot script cannot extract the root filesystem.

build-image.sh

@@ -104,7 +104,10 @@ apt-get install -y \
     vim \
     less \
     rsync \
-    git
+    git \
+    squashfs-tools \
+    wget \
+    curl
 
 # Clean up
 apt-get clean