Reduce image size for lazy installation packages (sonic-net#10775)

Why I did it
The image size is too large, when there are multiple lazy packages and multiple platforms. It is not necessary to keep the lazy installation packages in multiple copies.
For cisco image, the image size will reduce from 3.5G to 1.7G.

How I did it
Use symbol links to only keep one package for each of the lazy package.
Make a new folder fsroot/platform/common
Copy the lazy packages into the folder.
When using a package in each of the platform, such as x86_64-grub, x86_64-8800_rp-r0, x86_64-8201_on-r0, etc, only make a symbol link to the package in the common folder.

Author: xumia

build_debian.sh

@@ -643,5 +643,5 @@ fi
 pushd $FILESYSTEM_ROOT && sudo tar czf $OLDPWD/$FILESYSTEM_DOCKERFS -C ${DOCKERFS_PATH}var/lib/docker .; popd
 
 ## Compress together with /boot, /var/lib/docker and $PLATFORM_DIR as an installer payload zip file
-pushd $FILESYSTEM_ROOT && sudo zip $OLDPWD/$ONIE_INSTALLER_PAYLOAD -r boot/ $PLATFORM_DIR/; popd
+pushd $FILESYSTEM_ROOT && sudo zip --symlinks $OLDPWD/$ONIE_INSTALLER_PAYLOAD -r boot/ $PLATFORM_DIR/; popd
 sudo zip -g -n .squashfs:.gz $ONIE_INSTALLER_PAYLOAD $FILESYSTEM_SQUASHFS $FILESYSTEM_DOCKERFS

files/build_templates/sonic_debian_extension.j2

@@ -610,7 +610,9 @@ sudo LANG=C chroot $FILESYSTEM_ROOT depmod -a {{kversion}}
 sudo dpkg --root=$FILESYSTEM_ROOT -i {{deb}} || sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install -f --download-only
 
 sudo mkdir -p $FILESYSTEM_ROOT/$PLATFORM_DIR/{{dev}}
-sudo cp {{ deb }} $FILESYSTEM_ROOT/$PLATFORM_DIR/{{dev}}/
+sudo mkdir -p $FILESYSTEM_ROOT/$PLATFORM_DIR/common
+sudo cp {{ deb }} $FILESYSTEM_ROOT/$PLATFORM_DIR/common/
+sudo ln -sf "../common/{{ debfilename }}" "$FILESYSTEM_ROOT/$PLATFORM_DIR/{{dev}}/{{ debfilename }}"
 for f in $(find $FILESYSTEM_ROOT/var/cache/apt/archives -name "*.deb"); do
     sudo mv $f $FILESYSTEM_ROOT/$PLATFORM_DIR/{{dev}}/
 done