build: make it pass shellcheck

Without that fix, running 'shellcheck -x build' produces the following
errors/warnings:
    In build line 25:
    [ "x${DEBUG+set}" = 'xset' ] && set -v
      ^-------------^ SC2268 (style): Avoid x-prefix in comparisons
                                      as it no longer serves a purpose.
    In build line 131:
    resources/packages/"${package}"/"${task}" $@
                                              ^-- SC2068 (error):
    Double quote array expansions to avoid re-splitting elements.

    In build line 138:
    "${pkg_dir}"/"${task}" $@
                           ^-- SC2068 (error):
    Double quote array expansions to avoid re-splitting elements.

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
Acked-by: Adrien 'neox' Bourmault <neox@gnu.org>

build

@@ -22,7 +22,7 @@
 #
 ./.gitcheck
 
-[ "x${DEBUG+set}" = 'xset' ] && set -v
+[ "${DEBUG+set}" = 'set' ] && set -v
 set -u -e
 
 projectname="$(cat projectname)"
@@ -127,6 +127,7 @@ if [ $# -gt 1 ]; then
 			;;
 		all)
 			for package in $(list_packages "${task}"); do
+				# shellcheck disable=SC2068
 				resources/packages/"${package}"/"${task}" $@
 			done
 			;;
@@ -134,6 +135,7 @@ if [ $# -gt 1 ]; then
 			if [ -d resources/packages/"${package}" ] ; then
 				pkg_dir=resources/packages/"${package}"
 				if [ -f "${pkg_dir}"/"${task}" ]; then
+					# shellcheck disable=SC2068
 					"${pkg_dir}"/"${task}" $@
 				else
 					help

tests/lint

@@ -41,6 +41,7 @@ printf "+---------------------+\n"
 printf "| Running lint tests: |\n"
 printf "+---------------------+\n"
 run_shellcheck \
+    build \
     resources/packages/descriptors/distclean \
     resources/packages/flashrom/distclean \
     resources/packages/grub/distclean \