tools: add target_dec_fate.sh

Script to download and test ossfuzz testcases
This also includes a list of such testcases.
I intend to subsequently fill this list with the cases we have fixed in the past
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

tools/target_dec_fate.list

+544/clusterfuzz-testcase-5936536407244800.f8bd9b24_8ba77916_70c2c7be_3df6a2ea_96cd9f14          target_dec_interplay_video_fuzzer
+724/clusterfuzz-testcase-6738249571631104                                                       target_dec_pictor_fuzzer
+1214/clusterfuzz-testcase-minimized-6130606599569408                                            target_dec_h264_fuzzer
+5264/clusterfuzz-testcase-minimized-4621956621008896                                            target_dec_indeo5_fuzzer
+7279/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_G2M_fuzzer-5977332473921536              target_dec_g2m_fuzzer
+10053/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PROSUMER_fuzzer-5636993883570176        target_dec_prosumer_fuzzer

tools/target_dec_fate.sh

+#!/bin/sh
+#
+# * Copyright (C) 2018 Michael Niedermayer (michaelni@gmx.at)
+# *
+# * This file is part of FFmpeg.
+# *
+# * FFmpeg is free software; you can redistribute it and/or modify
+# * it under the terms of the GNU General Public License as published by
+# * the Free Software Foundation; either version 2 of the License, or
+# * (at your option) any later version.
+# *
+# * FFmpeg is distributed in the hope that it will be useful,
+# * but WITHOUT ANY WARRANTY; without even the implied warranty of
+# * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# * GNU General Public License for more details.
+# *
+# * You should have received a copy of the GNU General Public License
+# * along with FFmpeg; if not, write to the Free Software
+# * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+set -e
+
+LC_ALL=C
+export LC_ALL
+
+LIST=target_dec_fate.list
+
+show_help(){
+    cat <<EOF
+Usage: ./target_dec_fate.sh <directory> [<test to run>]
+
+directory       the directory into which sample files will be downloaded
+test to run     the number of the issue to test
+Note, some test samples may not yet be available to the public, also this
+script will not download samples which are already in the directory. So you
+may want to preserve its content between runs.
+EOF
+    exit 0
+}
+
+test -z "$1"  && show_help
+test ! -d "$1"  && echo $1 is not an accessable directory && show_help
+test ! -f target_dec_fate.sh && echo $0 Must be run from its location && show_help
+grep 'CONFIG_OSSFUZZ 0' ../config.h && echo not configured for ossfuzz && show_help
+
+#Download testcases
+while read -r LINE; do
+    ISSUE_NUM=`echo $LINE | sed 's#/.*##'`
+    FILE_ID=`echo $LINE | sed 's#.*/clusterfuzz-testcase[a-zA-Z0-9_-]*-\([0-9]*\).*#\1#'`
+    FILE=`echo $LINE | sed 's# .*##'`
+    if test -f "$1/$FILE" ; then
+        echo exists       $FILE
+    else
+        echo downloading  $FILE
+        mkdir -p "$1/$ISSUE_NUM"
+        wget -O "$1/$FILE" "https://oss-fuzz.com/download?testcase_id=$FILE_ID" || rm "$1/$FILE"
+    fi
+done < "$LIST"
+
+#Find which fuzzers we need to build
+TOOLS=
+while read -r LINE; do
+    TOOL_ID=`echo $LINE | sed 's#[^ ]* ##'`
+    TOOLS="$TOOLS tools/$TOOL_ID"
+done < "$LIST"
+
+cd ..
+#Build fuzzers
+make -j4 $TOOLS
+
+#Run testcases
+while read -r LINE; do
+    TOOL_ID=`echo $LINE | sed 's#[^ ]* ##'`
+    FILE=`echo $LINE | sed 's# .*##'`
+    tools/$TOOL_ID $1/$FILE
+done < "tools/$LIST"
+
+echo OK