Using the directory cmd/flux/manifests as a prerequisite causes a
problem: if the script that creates the files within fails, the next
invocation of make will see the directory and assume it
succeeded. Since the executable expects certain files to be present,
but they are not explicit prerequisites of the recipe for building the
binary, this results in a successful build but a broken `flux`
executable.

Instead, depend on a file that's explicitly updated when the script
has succeeded, and which itself depends on the inputs.

A couple of the CI workflows run

    make cmd/flux/manifests

before doing other things, presumably as a way to avoid running the
whole test suite in a CI pipeline for some purpose other than testing,
so these needed changing as well.

Signed-off-by: Michael Bridgen <michael@weave.works>

	Addresses: #1135

	Follow https://www.starfallprojects.co.uk/posts/deploy-mkdocs-netlify/


	to eventually fix #1135.

	I realise this litters the main directory somewhat, but I hope
	that once the publication fully works and we turn the site into
	redirects, we can remove these files again. So only a temporary
	measure.

Signed-off-by: Daniel Holbach <daniel@weave.works>

Signed-off-by: Hidde Beydals <hello@hidde.co>

- add make target for generating the install manifests using kustomize
- embed the generated manifests in flux binary
- the install and bootstrap commands default to using the embedded manifests
- download the install manifests from GitHub only if the install/bootstrap version arg is set

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>