Fixing several ShellCheck warnings

packaging/osx/buildpackage.sh

@@ -12,12 +12,12 @@ fi
 LAUNCHER_TAG="osx-launcher-20171118"
 
 if [ $# -ne "2" ]; then
-	echo "Usage: `basename $0` tag outputdir"
+	echo "Usage: $(basename "$0") tag outputdir"
     exit 1
 fi
 
 # Set the working dir to the location of this script
-cd $(dirname $0)
+cd "$(dirname "$0")" || exit 1
 
 TAG="$1"
 OUTPUTDIR="$2"
@@ -44,10 +44,10 @@ populate_template() {
 
 # Deletes from the first argument's mod dirs all the later arguments
 delete_mods() {
-	pushd "${BUILTDIR}/${1}/Contents/Resources/mods" > /dev/null
+	pushd "${BUILTDIR}/${1}/Contents/Resources/mods" > /dev/null || exit 1
 	shift
-	rm -rf $@
-	pushd > /dev/null
+	rm -rf "$@"
+	pushd > /dev/null || exit 1
 }
 
 echo "Building launchers"
@@ -70,12 +70,12 @@ modify_plist "{DEV_VERSION}" "${TAG}" "${BUILTDIR}/OpenRA.app/Contents/Info.plis
 modify_plist "{FAQ_URL}" "http://wiki.openra.net/FAQ" "${BUILTDIR}/OpenRA.app/Contents/Info.plist"
 echo "Building core files"
 
-pushd ${SRCDIR} > /dev/null
+pushd "${SRCDIR}" > /dev/null || exit 1
 make osx-dependencies
 make core SDK="-sdk:4.5"
 make version VERSION="${TAG}"
 make install-core gameinstalldir="/Contents/Resources/" DESTDIR="${BUILTDIR}/OpenRA.app"
-popd > /dev/null
+popd > /dev/null || exit 1
 
 curl -s -L -O https://raw.githubusercontent.com/wiki/OpenRA/OpenRA/Changelog.md
 markdown Changelog.md > "${BUILTDIR}/OpenRA.app/Contents/Resources/CHANGELOG.html"
@@ -106,10 +106,10 @@ else
 	curl -s -L -O https://github.com/OpenRA/libdmg-hfsplus/archive/master.zip || exit 3
 	unzip -qq master.zip
 	rm master.zip
-	pushd libdmg-hfsplus-master > /dev/null
+	pushd libdmg-hfsplus-master > /dev/null || exit 1
 	cmake . > /dev/null
 	make > /dev/null
-	popd > /dev/null
+	popd > /dev/null || exit 1
 
 	if [[ ! -f libdmg-hfsplus-master/dmg/dmg ]] ; then
 		echo "libdmg-hfsplus compilation failed"