Add the script run by OSS-Fuzz

This script used to live in oss-fuzz repository itself (under
projects/wxwidgets), but it seems better to have it in the main
repository, as this will make modifying it, e.g. to add new fuzzers,
simpler.

tests/fuzz/ossfuzz.sh

@@ -0,0 +1,12 @@
+#!/bin/bash -eu
+
+# build project
+./configure --without-subdirs --disable-shared --disable-sys-libs --disable-gui LDFLAGS="$CXXFLAGS"
+make -j$(nproc)
+
+# build fuzzers
+$CXX $CXXFLAGS -o $OUT/zip tests/fuzz/zip.cpp \
+    $LIB_FUZZING_ENGINE `./wx-config --cxxflags --libs base`
+
+# and copy their corpora
+zip -j $OUT/zip_seed_corpus.zip tests/fuzz/corpus/zip/*