target-xtensa: add core importing script

This script copies configuration and gdb information from the xtensa
configuration overlay archive and registers new xtensa core.
Signed-off-by: NMax Filippov <jcmvbkbc@gmail.com>

target-xtensa/import_core.sh

+#! /bin/bash -e
+
+OVERLAY="$1"
+NAME="$2"
+FREQ=40000
+BASE=$(dirname "$0")
+TARGET="$BASE"/core-$NAME
+
+[ $# -ge 2 -a -f "$OVERLAY" ] || { cat <<EOF
+Usage: $0 overlay-archive-to-import core-name [frequency-in-KHz]
+    overlay-archive-to-import:  file name of xtensa-config-overlay.tar.gz
+                                to import configuration from.
+    core-name:                  QEMU name of the imported core. Must be valid
+                                C identifier.
+    frequency-in-KHz:           core frequency (40MHz if not specified).
+EOF
+exit
+}
+
+[ $# -ge 3 ] && FREQ="$3"
+mkdir -p "$TARGET"
+tar -xf "$OVERLAY" -C "$TARGET" --strip-components=1 \
+    --xform='s/core/core-isa/' config/core.h
+tar -xf "$OVERLAY" -O gdb/xtensa-config.c | \
+    sed -n '1,/*\//p;/pc/,/a15/p' > "$TARGET"/gdb-config.c
+NUM_REGS=$(grep XTREG "$TARGET"/gdb-config.c | wc -l)
+
+cat <<EOF > "${TARGET}.c"
+#include "cpu.h"
+#include "exec/exec-all.h"
+#include "exec/gdbstub.h"
+#include "qemu/host-utils.h"
+
+#include "core-$NAME/core-isa.h"
+#include "overlay_tool.h"
+
+static const XtensaConfig $NAME __attribute__((unused)) = {
+    .name = "$NAME",
+    .gdb_regmap = {
+        .num_regs = $NUM_REGS,
+        .reg = {
+#include "core-$NAME/gdb-config.c"
+        }
+    },
+    .clock_freq_khz = $FREQ,
+    DEFAULT_SECTIONS
+};
+
+REGISTER_CORE($NAME)
+EOF
+
+grep -q core-${NAME}.o "$BASE"/Makefile.objs || \
+    echo "obj-y += core-${NAME}.o" >> "$BASE"/Makefile.objs