Makefile: Allow installation of fiemap/fiewalk support tools

There's now a new make target called "install_tools" which would not run
by default on installation.

One can add "OPTIONAL_INSTALL_TARGETS=install_tools" into localconf to
install these by default.

fiewalk would be installed to sbin, as only root can run it, the other
goes to bin.

Gentoo can use this to optionally install these tools as a package
feature.

Signed-off-by: Kai Krakow <kai@kaishome.de>

contrib/gentoo/bees-9999.ebuild

@@ -22,7 +22,7 @@ PATCHES="
 LICENSE="GPL-3"
 SLOT="0"
 KEYWORDS=""
-IUSE=""
+IUSE="tools"
 
 COMMON_DEPEND="
 	>=sys-apps/util-linux-2.30.2
@@ -41,4 +41,9 @@ HTML_DOCS="README.html"
 src_prepare() {
 	default
 	echo LIBDIR=$(get_libdir) >>${S}/localconf
+	localconf=${S}/localconf
+	if use tools; then
+		einfo "Building with support tools fiemap and fiewalk."
+		echo OPTIONAL_INSTALL_TARGETS=install_tools >>${localconf} || die
+	fi
 }