kheaders: rename the 'cpio_dir' variable to 'tmpdir'

The next commit will get rid of the use of 'cpio' command, as there is
no strong reason to use it just for copying files.

Before that, this commit renames the 'cpio_dir' variable to 'tmpdir'.

No functional changes are intended.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

kernel/gen_kheaders.sh

@@ -7,7 +7,7 @@ set -e
 sfile="$(readlink -f "$0")"
 outdir="$(pwd)"
 tarfile=$1
-cpio_dir=$outdir/${tarfile%/*}/.tmp_cpio_dir
+tmpdir=$outdir/${tarfile%/*}/.tmp_dir
 
 dir_list="
 include/
@@ -65,15 +65,15 @@ fi
 
 echo "  GEN     $tarfile"
 
-rm -rf $cpio_dir
-mkdir $cpio_dir
+rm -rf "${tmpdir}"
+mkdir "${tmpdir}"
 
 if [ "$building_out_of_srctree" ]; then
 	(
 		cd $srctree
 		for f in $dir_list
 			do find "$f" -name "*.h";
-		done | cpio --quiet -pd $cpio_dir
+		done | cpio --quiet -pd "${tmpdir}"
 	)
 fi
 
@@ -81,23 +81,23 @@ fi
 # of tree builds having stale headers in srctree. Just silence CPIO for now.
 for f in $dir_list;
 	do find "$f" -name "*.h";
-done | cpio --quiet -pdu $cpio_dir >/dev/null 2>&1
+done | cpio --quiet -pdu "${tmpdir}" >/dev/null 2>&1
 
 # Always exclude include/generated/utsversion.h
 # Otherwise, the contents of the tarball may vary depending on the build steps.
-rm -f "${cpio_dir}/include/generated/utsversion.h"
+rm -f "${tmpdir}/include/generated/utsversion.h"
 
 # Remove comments except SDPX lines
-find $cpio_dir -type f -print0 |
+find "${tmpdir}" -type f -print0 |
 	xargs -0 -P8 -n1 perl -pi -e 'BEGIN {undef $/;}; s/\/\*((?!SPDX).)*?\*\///smg;'
 
 # Create archive and try to normalize metadata for reproducibility.
 tar "${KBUILD_BUILD_TIMESTAMP:+--mtime=$KBUILD_BUILD_TIMESTAMP}" \
     --owner=0 --group=0 --sort=name --numeric-owner --mode=u=rw,go=r,a+X \
-    -I $XZ -cf $tarfile -C $cpio_dir/ . > /dev/null
+    -I $XZ -cf $tarfile -C "${tmpdir}/" . > /dev/null
 
 echo $headers_md5 > kernel/kheaders.md5
 echo "$this_file_md5" >> kernel/kheaders.md5
 echo "$(md5sum $tarfile | cut -d ' ' -f1)" >> kernel/kheaders.md5
 
-rm -rf $cpio_dir
+rm -rf "${tmpdir}"