board/sifive/hifive-unleashed: fix shellcheck warning in post-build.sh

This removes a warning reported by shellcheck: "Double quote to prevent
globbing and word splitting". As a result, the file can be removed from
.checkpackageignore.

Signed-off-by: Francois Dugast <francois.dugast.foss@gmail.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

.checkpackageignore

@@ -72,7 +72,6 @@ board/roseapplepi/patches/uboot/0001-compiler-.h-sync-include-linux-compiler-.h-
 board/roseapplepi/post-build.sh Shellcheck
 board/seeed/stm32mp157c-odyssey/patches/linux/0001-ARM-dts-stm32-fix-stm32mp157c-odyssey-card-detect.patch lib_patch.Upstream
 board/sheevaplug/patches/uboot/0001-Remove-redundant-YYLOC-global-declaration.patch lib_patch.Upstream
-board/sifive/hifive-unleashed/post-build.sh Shellcheck
 board/solidrun/clearfog/post-build.sh Shellcheck
 board/solidrun/macchiatobin/post-build-mainline.sh Shellcheck
 board/solidrun/macchiatobin/post-build.sh Shellcheck

board/sifive/hifive-unleashed/post-build.sh

@@ -1,2 +1,2 @@
 #!/bin/sh
-cp $BINARIES_DIR/boot.scr $TARGET_DIR/boot/boot.scr
+cp "$BINARIES_DIR/boot.scr" "$TARGET_DIR/boot/boot.scr"