build: `make check`: use a PATH search instead for Kyua

[kevans]

Summary

which(1) accepts both relative/absolute paths as well as lone binary
names. Set KYUA to kyua and use which(1) to confirm that it can find one;
if it cannot, just advise the user to set KYUA directly to the kyua binary
rather than assuming a relative location from LOCALBASE.

This allows make check to be operated with the version of kyua in base
without losing the flexibility of specifying another one.

[kevans]

Add in the problem we're solving; wanting to use kyua in base.

[ngie]

The reason why I hardcoded the path was to reduce redundant $PATH lookups and to ensure that random kyua(1) binaries wouldn't get picked up from someone's environment, increasing overall determinism of the target.

I prefer the old method, but also acknowledge that making this work more out of the box is more important for widespread adoption of the target.

share/mk/suite.test.mk

98

Grammar nit: e.g. must be followed by a comma: , e.g., .

[emaste]

I just ran into this issue and ended up making an equivalent fix in my tree.