POSIX 7.
Special target.
Keeps given intermediate build files.
Test:
make a.tmp
With precious: both a.tmp and a.tmp2 are created.
Without: a.tmp2 is created but gets removed afterwards. You can observe this with make --dry-run a.tmp which shows:
touch a.tmp2
touch a.tmp
rm b.tmp2
TODO understand better with more examples.