packaging: Make qemu/apply_patches.sh common

Moved the qemu/apply_patches.sh to the common scripts directory and
refactor it so that it can be used as a generic and consistent way
to apply patches.

Fixes #1014

Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>

tools/packaging/scripts/apply_patches.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+#
+# Copyright (c) 2020 Red Hat, Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# This script apply patches.
+#
+set -e
+
+script_dir="$(realpath $(dirname $0))"
+patches_dir="$1"
+
+if [ -z "$patches_dir" ]; then
+	cat <<-EOT
+	Apply patches to the sources at the current directory.
+
+	Patches are expected to be named in the standard git-format-patch(1) format where
+	the first part of the filename represents the patch ordering (lowest numbers
+	apply first):
+	    'NUMBER-DASHED_DESCRIPTION.patch'
+
+	For example,
+
+	    0001-fix-the-bad-thing.patch
+	    0002-improve-the-fix-the-bad-thing-fix.patch
+	    0003-correct-compiler-warnings.patch
+
+	Usage:
+	    $0 PATCHES_DIR
+	Where:
+	    PATCHES_DIR is the directory containing the patches
+	EOT
+	exit 1
+fi
+
+echo "INFO: Apply patches from $patches_dir"
+if [ -d "$patches_dir" ]; then
+	patches=($(find "$patches_dir" -name '*.patch'|sort -t- -k1,1n))
+	echo "INFO: Found ${#patches[@]} patches"
+	for patch in ${patches[@]}; do
+		echo "INFO: Apply $patch"
+		git apply "$patch" || \
+			{ echo >&2 "ERROR: Not applied. Exiting..."; exit 1; }
+	done
+else
+	echo "INFO: Patches directory does not exist"
+fi