package/opkg-utils: remove build step

opkg-utils is a package that only provides bash and python scripts.
Upon further inspection of the Makefile for the package, invoking
`make` only ever builds the manpage. The previous commit dropped the
installation of the manpage. This makes the build step unnecessary so
remove it.

Add a comment to explain the situation

Signed-off-by: Ryan Barnett <ryan.barnett@rockwellcollins.com>
[yann.morin.1998@free.fr: reword commit log]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 05bf014f56c0c99f08c93db7829e8fd53af3c9a8)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/opkg-utils/opkg-utils.mk

@@ -12,10 +12,7 @@ OPKG_UTILS_LICENSE_FILES = COPYING
 
 HOST_OPKG_UTILS_DEPENDENCIES += $(BR2_PYTHON3_HOST_DEPENDENCY)
 
-define HOST_OPKG_UTILS_BUILD_CMDS
-	$(MAKE) -C $(@D) $(HOST_CONFIGURE_OPTS)
-endef
-
+# Nothing to build; only scripts to install.
 define HOST_OPKG_UTILS_INSTALL_CMDS
 	$(MAKE) -C $(@D) PREFIX=$(HOST_DIR) install-utils
 endef