In running Make, I find targets being remade that shouldn't have to be
remade; being considered younger than the prerequisites from which
they've just been made. It seems to happen especially with
prerequisites created by `touch`: e.g.:
$ cat Makefile
all : bar baz
bar baz : foo
cp $< $@
foo :
touch $@
$ rm foo bar baz
$ make
touch foo
cp foo bar
cp foo baz
$ make
cp foo bar
cp foo baz
$ make
cp foo bar
cp foo baz
$ make
cp foo bar
cp foo baz
$ make
cp foo bar
cp foo baz
$ make
cp foo bar
$ make
make: Nothing to be done for `all'.
Sleeping helps, but you have to sleep for quite a while; even 2 seconds
may not be enough: