Allows a template to define in which circumstances its do_check phase
should run, without requiring custom do_check definitions in each
template (also makes it easier to change how build styles do things
without checking as many templates).
Add to Manual and CONTRIBUTING as well.
Add another stage 'check' between 'build' and 'install'. It is be enabled using the
variable XBPS_CHECK_PKGS=yes and disabled if unset, set to "0" or "no" in your
local etc/conf.
A new xbps-src option `-q` for `quick` will disable XBPS_CHECK_PKGS by overriding it to 0.
If enabled, `common/xbps-src/shutils/xbps-src-docheck.sh` checks for an existing
`do_check()` function in the package's template and, if it exists, calls it.
A new template variable `checkdepends` may be present and list packages required
to run the `do_check()` function. Example: `checkdepends="bc unittest-cpp"`.
