Remove apt cache and skip recommended packages
This reduces the layer size from 367MiB to 178MiB.
BEFORE:
```
$ docker history ea2d6da4cbdc
IMAGE CREATED CREATED BY SIZE COMMENT
ea2d6da4cbdc 27 seconds ago /bin/sh -c #(nop) ENTRYPOINT ["/entrypoint.… 0B
2c7e3f0de3c8 27 seconds ago /bin/sh -c #(nop) COPY file:ad76fe44d1402628… 1.44kB
1a29ca960363 29 seconds ago /bin/sh -c apt-get update && apt-get install… 367MB
f643c72bc252 12 days ago /bin/sh -c #(nop) CMD ["/bin/bash"] 0B
<missing> 12 days ago /bin/sh -c mkdir -p /run/systemd && echo 'do… 7B
<missing> 12 days ago /bin/sh -c [ -z "$(apt-get indextargets)" ] 0B
<missing> 12 days ago /bin/sh -c set -xe && echo '#!/bin/sh' > /… 811B
<missing> 12 days ago /bin/sh -c #(nop) ADD file:4f15c4475fbafb3fe… 72.9MB
```
AFTER:
```
$ docker history c96da58d5a74
IMAGE CREATED CREATED BY SIZE COMMENT
c96da58d5a74 5 seconds ago /bin/sh -c #(nop) ENTRYPOINT ["/entrypoint.… 0B
b821a8d478a9 5 seconds ago /bin/sh -c #(nop) COPY file:ad76fe44d1402628… 1.44kB
ac4b2f30261d 5 seconds ago /bin/sh -c apt-get update && apt-get instal… 178MB
f643c72bc252 12 days ago /bin/sh -c #(nop) CMD ["/bin/bash"] 0B
<missing> 12 days ago /bin/sh -c mkdir -p /run/systemd && echo 'do… 7B
<missing> 12 days ago /bin/sh -c [ -z "$(apt-get indextargets)" ] 0B
<missing> 12 days ago /bin/sh -c set -xe && echo '#!/bin/sh' > /… 811B
<missing> 12 days ago /bin/sh -c #(nop) ADD file:4f15c4475fbafb3fe… 72.9MB
```
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