varnish: update to 6.3.0.

Adds Varnish back to packages.

  - Don't use jemalloc on -musl builds. This appears to be leading to
    the segfault described in the earlier broken= message for those.
    Noticed the segfault doesn't happen in Alpine's build, and the only
    major difference there is that they disable jemalloc (because they
    don't support it, but given that it's the only difference, it was
    worth disabling to get builds working).

    jemalloc remains enabled for glibc.

  - Disable pcrejit by default. There is a build option to turn it on,
    but this is disabled by default for cross builds. We could add
    a check for target machine == host machine and enable it on those
    by default if desired, but the build option may be easier. Could
    also hack around the config cache, but I'm less confident in JIT
    availability on ARM and such than I am basic socket definitions.

  - The package originally included a varnish-vcl-reload file in the
    files directory. This has been removed because it is, as far as
    I can tell, unused.

  - Rewrite run file. Old one doesn't work at all, no reason to
    preserve it.

  - Add _varnish and _vcache system users for default jail argument in
    run file. These share a system group.

common/shlibs

@@ -3515,3 +3515,4 @@ libnozzle.so.1 libnozzle1-1.11_2
 libmygpo-qt5.so.1 libmygpo-qt-1.1.0_1
 libluv.so.1 libluv-1.30.1.0_1
 libarmadillo.so.9 armadillo-9.700.2_1
+libvarnishapi.so.2 libvarnishapi-6.3.0_1