lz4 --rm on Ubuntu 18.04 (Add LZ4 compression to pg_dump)

Re: Tomas Vondra
> Add LZ4 compression to pg_dump

This broke the TAP tests on Ubuntu 18.04 (bionic):

[17:06:45.513](0.000s) ok 1927 - compression_lz4_custom: should not dump test_table with 4-row INSERTs
# Running: pg_dump --jobs=2 --format=directory --compress=lz4:1 --file=/home/myon/projects/postgresql/pg/master/build/src/bin/pg_dump/tmp_check/tmp_test__aAO/compression_lz4_dir postgres
[17:06:46.651](1.137s) ok 1928 - compression_lz4_dir: pg_dump runs
# Running: /usr/bin/lz4 -z -f --rm /home/myon/projects/postgresql/pg/master/build/src/bin/pg_dump/tmp_check/tmp_test__aAO/compression_lz4_dir/blobs.toc /home/myon/projects/postgresql/pg/master/build/src/bin/pg_dump/tmp_check/tmp_test__aAO/compression_lz4_dir/blobs.toc.lz4
Incorrect parameters
Usage :
/usr/bin/lz4 [arg] [input] [output]

input : a filename
with no FILE, or when FILE is - or stdin, read standard input
Arguments :
-1 : Fast compression (default)
-9 : High compression
-d : decompression (default for .lz4 extension)
-z : force compression
-f : overwrite output without prompting
-h/-H : display help/long help and exit
[17:06:46.667](0.016s) not ok 1929 - compression_lz4_dir: compression commands
[17:06:46.668](0.001s)
[17:06:46.668](0.001s) # Failed test 'compression_lz4_dir: compression commands'
[17:06:46.669](0.000s) # at t/002_pg_dump.pl line 4274.
[17:06:46.670](0.001s) ok 1930 - compression_lz4_dir: glob check for /home/myon/projects/postgresql/pg/master/build/src/bin/pg_dump/tmp_check/tmp_test__aAO/compression_lz4_dir/toc.dat

The lz4 binary there doesn't have the --rm option yet.

liblz4-tool 0.0~r131-2ubuntu3

--rm appears in a single place only:

# Give coverage for manually compressed blob.toc files during
# restore.
compress_cmd => {
program => $ENV{'LZ4'},
args => [
'-z', '-f', '--rm',
"$tempdir/compression_lz4_dir/blobs.toc",
"$tempdir/compression_lz4_dir/blobs.toc.lz4",
],
},

18.04 will be EOL in a few weeks so it might be ok to just say it's
not supported, but removing the input file manually after calling lz4
would be an easy fix.

Christoph