Build dependencies cannot be hidden

[ocaisa]

(Transferred from easybuilders/easybuild-easyconfigs#1883)

The following in an easyconfig will not work:

# zlib required, but being linked instatically, so not a runtime dep
builddependencies = [('zlib', '1.2.8')]
hiddendependencies = [('zlib', '1.2.8')]

This results in:

-bash-4.2$ eb --force --hidden ./binutils-2.25.eb 
== temporary log file in case of crash /tmp/eb-KYLZRy/easybuild-Ydxdg_.log
ERROR: Failed to process easyconfig /homeb/zam/swmanage/BINUTILS/binutils-2.25.eb: Hidden dependencies with visible module names ['Core/zlib/1.2.8'] not in list of dependencies: []

[boegel]

I just realised that this would be very useful to hide the modules that are needed to bootstrap the GCC+binutils combo in the GNU toolchain; it's one of the few locations where marking dependencies as hidden by default makes sense

[boegel]

Not trivial due to this (copy-pasted from easybuilders/easybuild-easyconfigs#1883):

Hmm, I guess we should simply relax the requirement and also accept that hidden dependencies are included in builddependencies. This does complicate dumping the easyconfig though, since hiddendependencies need to be restored in either dependencies or builddependencies then. See #1354.

Maybe we can simply introduce hiddenbuilddependencies, but I don't like where this is going...

[JackPerdue]

As I sit here pondering my own variation on the above mentioned bootstrap (which now gets up to binutilsbase/2.25-gccbase-4.8.4-binutilsbase-2.25-gccbase-4.4.7-11.el6 before I build a 'GCC' [be grateful I didn't include the RHEL6 binutils version in there too]), we really need this. Hiddendeps are great but so long as they are forced into deps and not simply builddeps, it makes it hard to make the last jump where I can hide the bases from the user.

/me casts two votes (two hands up) for '''hiddenbuilddependencies'''.

[JackPerdue]

Note that this especially makes sense on the BG/Q where everything is usually compiled statically anyway (no runtime deps).

[boegel]

a fix for this is in #1503, let's follow up there (I want to avoid having duplicate issues open)