Infrastructure changes to allow unsetting template vars/funcs.

xbps-src-112 does not unset those vars/funcs anymore, so it's a work
that must be done via common/environment/setup{,-subpkg}.

common/hooks/post-install/03-strip-and-debug-pkgs.sh

@@ -105,7 +105,7 @@ hook() {
 				return 1
 			fi
 			echo "   Stripped library: ${f#$PKGDESTDIR}"
-			_soname=$(objdump -p "$f"|grep SONAME|awk '{print $2}')
+			_soname=$(${OBJDUMP} -p "$f"|grep SONAME|awk '{print $2}')
 			if [ -n "${_soname}" ]; then
 				echo "${_soname}" >> ${PKGDESTDIR}/.shlib-provides
 			fi

common/hooks/post-install/06-prepare-32bit.sh

@@ -113,6 +113,4 @@ hook() {
 		printf "${pkgver} " >> ${destdir32}/rdeps
 	fi
 	printf "\n" >> ${destdir32}/rdeps
-
-	unset lib32depends lib32disabled lib32files lib32mode
 }