Publish shasum cli compatible hash files

[ronanchilvers]

Currently the hash files published with each binary release are in a format that isn't consumable by the shasum perl script (that is commonly distributed with many Linux distributions and platforms) when using its --check option. When automating the download and hash check of a new version, there is some unpleasant parsing and rewriting of the current *_hashes.txt files to create a format which can be read correctly by shasum --check.

It would be really useful if binary releases could include an additional hash file in a shasum compatible format. From the shasum man page:

When verifying SHA-512/224 or SHA-512/256 checksums, indicate the
algorithm explicitly using the -a option, e.g.

shasum -a 512224 -c checksumfile

The sums are computed as described in FIPS PUB 180-4. When checking,
the input should be a former output of this program. The default
mode is to print a line with checksum, a character indicating type
(*' for binary, ' for text, U' for UNIVERSAL, ^' for BITS),
and name for each FILE. The line starts with a \' character if the FILE name contains either newlines or backslashes, which are then replaced by the two-character sequences \n' and `\' respectively.

The file can be generated by shasum itself to ensure the format is correct. A simple example (note this uses the default sha1 but other algorithms are supported):

$ touch testfile.txt
$ shasum testfile.txt
da39a3ee5e6b4b0d3255bfef95601890afd80709  testfile.txt
$ shasum testfile.txt > shasums.txt
$ shasum --check shasums.txt
testfile.txt: OK
$ cat shasums.txt
da39a3ee5e6b4b0d3255bfef95601890afd80709  testfile.txt