scripts: Use $(..) instead of deprecated `..`

This fixes these warnings from shellcheck:

    ^-- SC2006: Use $(..) instead of deprecated `..`

Update also a comment using the same pattern.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

scripts/clean-includes

@@ -39,7 +39,7 @@
 # However some caution is required regarding files that might be part
 # of the guest agent or standalone tests.
 
-# for i in `git ls-tree --name-only HEAD`  ; do test -f $i && \
+# for i in $(git ls-tree --name-only HEAD) ; do test -f $i && \
 #   grep -E '^# *include' $i | head -1 | grep 'osdep.h' ; test $? != 0 && \
 #   echo $i ; done
 

scripts/create_config

@@ -16,7 +16,7 @@ case $line in
  qemu_*dir=*) # qemu-specific directory configuration
     name=${line%=*}
     value=${line#*=}
-    define_name=`echo $name | LC_ALL=C tr '[a-z]' '[A-Z]'`
+    define_name=$(echo $name | LC_ALL=C tr '[a-z]' '[A-Z]')
     eval "define_value=\"$value\""
     echo "#define CONFIG_$define_name \"$define_value\""
     # save for the next definitions
@@ -72,7 +72,7 @@ case $line in
     ;;
  ARCH=*) # configuration
     arch=${line#*=}
-    arch_name=`echo $arch | LC_ALL=C tr '[a-z]' '[A-Z]'`
+    arch_name=$(echo $arch | LC_ALL=C tr '[a-z]' '[A-Z]')
     echo "#define HOST_$arch_name 1"
     ;;
  HOST_USB=*)
@@ -92,7 +92,7 @@ case $line in
     ;;
  TARGET_BASE_ARCH=*) # configuration
     target_base_arch=${line#*=}
-    base_arch_name=`echo $target_base_arch | LC_ALL=C tr '[a-z]' '[A-Z]'`
+    base_arch_name=$(echo $target_base_arch | LC_ALL=C tr '[a-z]' '[A-Z]')
     echo "#define TARGET_$base_arch_name 1"
     ;;
  TARGET_XML_FILES=*)

scripts/feature_to_c.sh

@@ -33,7 +33,7 @@ if test -e "$output"; then
 fi
 
 for input; do
-  arrayname=xml_feature_`echo $input | sed 's,.*/,,; s/[-.]/_/g'`
+  arrayname=xml_feature_$(echo $input | sed 's,.*/,,; s/[-.]/_/g')
 
   ${AWK:-awk} 'BEGIN { n = 0
       printf "#include \"qemu/osdep.h\"\n"
@@ -67,8 +67,8 @@ echo >> $output
 echo "const char *const xml_builtin[][2] = {" >> $output
 
 for input; do
-  basename=`echo $input | sed 's,.*/,,'`
-  arrayname=xml_feature_`echo $input | sed 's,.*/,,; s/[-.]/_/g'`
+  basename=$(echo $input | sed 's,.*/,,')
+  arrayname=xml_feature_$(echo $input | sed 's,.*/,,; s/[-.]/_/g')
   echo "  { \"$basename\", $arrayname }," >> $output
 done
 

scripts/make_device_config.sh

@@ -7,7 +7,7 @@
 src=$1
 dep=$2
 target=$3
-src_dir=`dirname $src`
+src_dir=$(dirname $src)
 all_includes=
 
 process_includes () {
@@ -20,7 +20,7 @@ process_includes () {
 
 f=$src
 while [ -n "$f" ] ; do
-  f=`cat $f | tr -d '\r' | awk '/^include / {printf "'$src_dir'/%s ", $2}'`
+  f=$(cat $f | tr -d '\r' | awk '/^include / {printf "'$src_dir'/%s ", $2}')
   [ $? = 0 ] || exit 1
   all_includes="$all_includes $f"
 done

scripts/qemu-binfmt-conf.sh

@@ -10,7 +10,7 @@ if [ ! -f /proc/sys/fs/binfmt_misc/register ]; then
 fi
 
 # probe cpu type
-cpu=`uname -m`
+cpu=$(uname -m)
 case "$cpu" in
   i386|i486|i586|i686|i86pc|BePC|x86_64)
     cpu="i386"

scripts/update-linux-headers.sh

@@ -10,7 +10,7 @@
 # This work is licensed under the terms of the GNU GPL version 2.
 # See the COPYING file in the top-level directory.
 
-tmpdir=`mktemp -d`
+tmpdir=$(mktemp -d)
 linux="$1"
 output="$2"