[gdb/tdep] Improve gdb/syscalls/update-linux.sh

Fix two things in update-linux.sh:
- remove use of unnecessary tmp file
- inline gen-header.py into update-linux.sh

Tested on x86_64-linux.

---
 gdb/syscalls/gen-header.py   | 32 --------------------------------
 gdb/syscalls/update-linux.sh | 33 +++++++++++++++++++++++----------
 2 files changed, 23 insertions(+), 42 deletions(-)

diff --git a/gdb/syscalls/gen-header.py b/gdb/syscalls/gen-header.py
deleted file mode 100644
index 78ccdddbff6..00000000000
--- a/gdb/syscalls/gen-header.py
+++ /dev/null
@@ -1,32 +0,0 @@
-# Copyright (C) 2013-2022 Free Software Foundation, Inc.
-
-# Copying and distribution of this file, with or without modification,
-# are permitted in any medium without royalty provided the copyright
-# notice and this notice are preserved.  This file is offered as-is,
-# without any warranty.
-
-import sys
-import time
-
-infname = sys.argv[1]
-
-print(
-    """\
-<?xml version="1.0"?>
-<!-- Copyright (C) 2009-%s Free Software Foundation, Inc.
-
-     Copying and distribution of this file, with or without modification,
-     are permitted in any medium without royalty provided the copyright
-     notice and this notice are preserved.  -->
-
-<!DOCTYPE feature SYSTEM "gdb-syscalls.dtd">
-
-<!-- This file was generated using the following file:
-
-     %s
-
-     The file mentioned above belongs to the Linux Kernel.  -->
-
-"""
-    % (time.strftime("%Y"), infname)
-)
diff --git a/gdb/syscalls/update-linux.sh b/gdb/syscalls/update-linux.sh
index a6719077dc5..e26ec4e92cb 100755
--- a/gdb/syscalls/update-linux.sh
+++ b/gdb/syscalls/update-linux.sh
@@ -36,25 +36,38 @@ if [ ! -f "$f" ]; then
     exit 1
 fi
 
+year=$(date +%Y)
+
 (
-    python gen-header.py "<sys/syscall.h>"
+    cat <<EOF
+<?xml version="1.0"?>
+<!-- Copyright (C) 2009-$year Free Software Foundation, Inc.
 
-    tmp=$(mktemp)
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
 
-    echo '#include <sys/syscall.h>' \
-	| gcc -E - -dD "$@" \
-	| grep -E '#define __NR_' \
-		> "$tmp"
+<!DOCTYPE feature SYSTEM "gdb-syscalls.dtd">
+
+<!-- This file was generated using the following file:
+
+     <sys/syscall.h>
+
+     The file mentioned above belongs to the Linux Kernel.  -->
+
+
+EOF
 
     echo '<syscalls_info>'
 
-    while read -r line; do
+    echo '#include <sys/syscall.h>' \
+	| gcc -E - -dD "$@" \
+	| grep -E '#define __NR_' \
+	| while read -r line; do
 	name=$(echo "$line" | awk '{print $2}' | sed 's/^__NR_//')
 	nr=$(echo "$line" | awk '{print $3}')
 	echo "  <syscall name=\"$name\" number=\"$nr\"/>"
-    done < "$tmp"
+    done
 
     echo '</syscalls_info>'
-
-    rm -f "$tmp"
 ) > "$f"