it may be useful to have way of injecting direct flags into $LDFLAGS

[migueldiascosta]

At the toolchain level, EasyBuild treats LDFLAGS as LinkLibraryPaths

easybuild-framework/easybuild/tools/toolchain/constants.py

Lines 62 to 63 in dec669c

	LinkLibraryPaths: [
	('LDFLAGS', 'Flags passed to linker'), # TODO: overridden by command line?

which prepends -L

easybuild-framework/easybuild/tools/toolchain/variables.py

Lines 41 to 43 in f215ae5

	class LinkLibraryPaths(AbsPathList):
	"""Absolute path to directory containing libraries"""
	PREFIX = '-L'

However, in some cases (see #3677 (comment)) there are direct flags that set the library paths

It may then be useful to have a way of injecting direct flags in LDFLAGS