Cleanup of make dependencies to fix the parallell build races.

Cleanup of make dependencies to fix the parallell build races.

Actually the problem was quite basic, and also manifested itself on
the call to cf_gen.

The problematic rules look like:

target1 target2: some.dependency
	command wich makes both of target1 and target2

this is incompatible with make -j, as make assumes the command only
builds one of the targets (the one available in $@).

There are two ways to work around this. One is to make the command
only build one of the targets (as done in fs/ and repl/), the other to chain
dependencies between the two targets with some "magic" to have the first
target in the chain rebuilt in case it alone gets removed..

target1: target2
	@sh -c "test -f target1 || command to regenerate the targets"

target2: dependency
	command to regenerate the targets

Tested on RedHat Linux 6.2 (GNU Make) and FreeBSD 4.0.