[Issue 24584] [phobos] `make unittest` should not rerun tests unnecessarily

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24584

--- Comment #3 from Nick Treleaven <nick at geany.org> ---
> There are multiple existing options for running the unittests of a single module or package

Oh great, thanks. I completely missed that but I see now that .test is
mentioned at the top of the Makefile.

> *running* (not building) all Phobos unittests on my laptop takes about 6 (release) / 7.5 (debug) seconds

I have an old PC (I don't use -j as I only have 2 cores and 1 I keep for other
things):

time make unittest
...
make[1]: Leaving directory '/home/nick/git/phobos'

real    16m57.602s
user    15m21.911s
sys     1m0.822s

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