determine the toolchain generation in hooks

[smoors]

• determine the toolchain generation in hooks
• remove --toolchain option
• update tests

replaces #30

[lexming]

It seems that the dict returned by this method does not change during runtime. So it can be converted to a global constant.

Suggested change

	def get_tc_versions():
	" build dict of (sub)toolchain-versions per valid generation "
	tc_versions = {}
	for toolcgen in VALID_TCGENS:
	tc_versions[toolcgen] = []
	for toolc in VALID_TCS:
	try:
	tc_versions[toolcgen].extend(get_toolchain_hierarchy({'name': toolc, 'version': toolcgen}))
	except EasyBuildError:
	# skip if no easyconfig found for toolchain-version
	pass
	return tc_versions
	# dict of (sub)toolchain-versions per valid generation "
	TOOLCHAIN_VERSIONS = {}
	for toolcgen in VALID_TCGENS:
	TOOLCHAIN_VERSIONS[toolcgen] = []
	for toolc in VALID_TCS:
	try:
	TOOLCHAIN_VERSIONS[toolcgen].extend(get_toolchain_hierarchy({'name': toolc, 'version': toolcgen}))
	except EasyBuildError:
	# skip if no easyconfig found for toolchain-version
	pass

[smoors]

i thought about this at first, but if it is set globally it will be calculated for every hook,
whereas the function will run only once for each easyconfig