[Bug other/82704] New: GCC fails to download prerequisites on busybox distro (unrecognized sha512sum --check)

[keno at juliacomputing dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82704

            Bug ID: 82704
           Summary: GCC fails to download prerequisites on busybox distro
                    (unrecognized sha512sum --check)
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: keno at juliacomputing dot com
  Target Milestone: ---

The contrib/download_prerequisites script uses `sha512sum --check` to verify
the integrity
of the downloaded prerequisites. This is an alias for `-c` in coreutils, but
busybox does not recognize this alias, leading to the below failure (on an
Alpine Linux
based system). The solution is simply to replace `--check`, by `-c` which
should work on both coreutils and busybox. I have verified that with that
change, everything else goes through as usual.

```
Connecting to gcc.gnu.org (209.132.180.131:21)
gmp-6.1.0.tar.bz2      0% |                               | 12132   0:03:15 ETA
gmp-6.1.0.tar.bz2     23% |*******                        |   544k  0:00:06 ETA
gmp-6.1.0.tar.bz2     77% |***********************        |  1795k  0:00:00 ETA
gmp-6.1.0.tar.bz2    100% |*******************************|  2327k  0:00:00 ETA

Connecting to gcc.gnu.org (209.132.180.131:21)
mpfr-3.1.4.tar.bz2     6% |*                              | 82228   0:00:14 ETA
mpfr-3.1.4.tar.bz2    55% |*****************              |   693k  0:00:01 ETA
mpfr-3.1.4.tar.bz2   100% |*******************************|  1249k  0:00:00 ETA

Connecting to gcc.gnu.org (209.132.180.131:21)
mpc-1.0.3.tar.gz      26% |********                       |   172k  0:00:02 ETA
mpc-1.0.3.tar.gz     100% |*******************************|   654k  0:00:00 ETA

Connecting to gcc.gnu.org (209.132.180.131:21)
isl-0.16.1.tar.bz2     4% |*                              | 70096   0:00:22 ETA
isl-0.16.1.tar.bz2    35% |**********                     |   559k  0:00:03 ETA
isl-0.16.1.tar.bz2    95% |*****************************  |  1517k  0:00:00 ETA
isl-0.16.1.tar.bz2   100% |*******************************|  1588k  0:00:00 ETA

sha512sum: unrecognized option: check
BusyBox v1.26.2 (2017-06-11 06:38:32 GMT) multi-call binary.

Usage: sha512sum [-c[sw]] [FILE]...

Print or check SHA512 checksums

        -c      Check sums against list in FILEs
        -s      Don't output anything, status code shows success
        -w      Warn about improperly formatted checksum lines
error: Cannot verify integrity of possibly corrupted file gmp-6.1.0.tar.bz2
```