Recognize lib dirs that may be used later

This let you specify a bunch of directory names on the command line
to *all* packages, without getting annoying warnings that they are
defined but not used.

cmake/Modules/OpmKnown.cmake

@@ -0,0 +1,47 @@
+# -*- mode: cmake; tab-width: 2; indent-tabs-mode: t; truncate-lines: t; compile-command: "cmake -Wdev" -*-
+# vim: set filetype=cmake autoindent tabstop=2 shiftwidth=2 noexpandtab softtabstop=2 nowrap:
+
+# emulate the with-xxx feature of autotools to not give warnings
+# if we specify the directories of packages that are known to the
+# family but not necessarily used
+
+# pick package names from these; opm-xxx, dune-xxx
+set (KNOWN_FAMILIES
+	opm
+	dune
+	)
+
+# variables to test; xxx_DIR, xxx_ROOT
+set (KNOWN_VARS
+	DIR
+	ROOT
+	)
+
+set (KNOWN_opm_PKGS
+	autodiff
+	core
+	material
+	parser
+	polymer
+	porsol
+	upscaling
+	verteq
+	)
+
+set (KNOWN_dune_PKGS
+	common
+	cornerpoint
+	geometry
+	grid
+	istl
+	localfunctions
+	)
+
+foreach (family IN ITEMS ${KNOWN_FAMILIES})
+	foreach (package IN ITEMS ${KNOWN_${family}_PKGS})
+		foreach (var IN ITEMS ${KNOWN_VARS})
+			# just "use" the variable, so we don't get warnings
+			set (_dummy ${${family}-${package}_${var}})
+		endforeach (var)
+	endforeach (package)
+endforeach (family)