replace deprecated `...` syntax with $(...) in shell scripts

abuild-keygen.in

@@ -107,7 +107,7 @@ install_pubkey=
 non_interactive=
 quiet=
 
-args=`getopt -o ainqh --long append,install,quiet,help -n "$program" -- "$@"`
+args=$(getopt -o ainqh --long append,install,quiet,help -n "$program" -- "$@")
 if [ $? -ne 0 ]; then
 	usage
 	exit 2

abuild-sign.in

@@ -63,7 +63,7 @@ privkey="$PACKAGER_PRIVKEY"
 pubkey=
 quiet=
 
-args=`getopt -o ek:p:qh --long installed,private:,public:,quiet,help -n "$program" -- "$@"`
+args=$(getopt -o ek:p:qh --long installed,private:,public:,quiet,help -n "$program" -- "$@")
 if [ $? -ne 0 ]; then
 	usage
 	exit 2

abump.in

@@ -108,8 +108,8 @@ fixes=
 [ -n "$APORTSDIR" ] || error "can't locate \$APORTSDIR"
 git rev-parse 2>/dev/null || die "not in a git tree"
 
-args=`getopt -o f:s:Rkqh --long fixes:,security:,recursive,keep,quiet,help \
-	-n "$program" -- "$@"`
+args=$(getopt -o f:s:Rkqh --long fixes:,security:,recursive,keep,quiet,help \
+	-n "$program" -- "$@")
 if [ $? -ne 0 ]; then
 	usage
 	exit 2

apkgrel.in

@@ -95,8 +95,8 @@ force=
 setto=
 only_clean_git=
 
-args=`getopt -o zags:tfqh --long zero,add,clean-git,set:,test,force,quiet,help \
-	-n "$program" -- "$@"`
+args=$(getopt -o zags:tfqh --long zero,add,clean-git,set:,test,force,quiet,help \
+	-n "$program" -- "$@")
 if [ $? -ne 0 ]; then
 	usage
 	exit 2

bootchartd

@@ -178,7 +178,7 @@ stop-initfs)
 	cd "$LOGDIR"
 	mkdir "$NEWROOT$LOGDIR"
 	cp /sbin/bootchartd $NEWROOT/sbin
-	PID=`cat bootchart.pid`
+	PID=$(cat bootchart.pid)
 	kill -USR2 $PID
 	wait $PID
 	mv * "$NEWROOT$LOGDIR"