Vendored libslirp (#2045)

Add vendored libslirp into the repo with a shim to remove its dependency on glib.

src/frontend/libslirp/fuzzing/oss-fuzz.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+
+set -ex
+
+export CC=${CC:-clang}
+export CXX=${CXX:-clang++}
+export WORK=${WORK:-$(pwd)}
+export OUT=${OUT:-$(pwd)/out}
+
+build=$WORK/build
+rm -rf $build
+mkdir -p $build
+mkdir -p $OUT
+
+fuzzflag="oss-fuzz=true"
+if [ -z "$FUZZING_ENGINE" ]; then
+    fuzzflag="llvm-fuzz=true"
+fi
+
+meson $build \
+      -D$fuzzflag \
+      -Db_lundef=false \
+      -Ddefault_library=static \
+      -Dstatic=true \
+      -Dbuildtype=debugoptimized
+
+ninja -C $build
+
+zip -jqr $OUT/fuzz-arp_seed_corpus.zip "$(dirname "$0")/IN_arp"
+zip -jqr $OUT/fuzz-ip-header_seed_corpus.zip "$(dirname "$0")/IN_ip-header"
+zip -jqr $OUT/fuzz-udp_seed_corpus.zip "$(dirname "$0")/IN_udp"
+zip -jqr $OUT/fuzz-udp-h_seed_corpus.zip "$(dirname "$0")/IN_udp-h"
+zip -jqr $OUT/fuzz-tftp_seed_corpus.zip "$(dirname "$0")/IN_tftp"
+zip -jqr $OUT/fuzz-dhcp_seed_corpus.zip "$(dirname "$0")/IN_dhcp"
+zip -jqr $OUT/fuzz-icmp_seed_corpus.zip "$(dirname "$0")/IN_icmp"
+zip -jqr $OUT/fuzz-tcp_seed_corpus.zip "$(dirname "$0")/IN_tcp"
+zip -jqr $OUT/fuzz-tcp-h_seed_corpus.zip "$(dirname "$0")/IN_tcp-h"
+
+zip -jqr $OUT/fuzz-ndp_seed_corpus.zip "$(dirname "$0")/IN_ndp"
+zip -jqr $OUT/fuzz-ip6-header_seed_corpus.zip "$(dirname "$0")/IN_ip6-header"
+zip -jqr $OUT/fuzz-udp6_seed_corpus.zip "$(dirname "$0")/IN_udp6"
+zip -jqr $OUT/fuzz-udp6-h_seed_corpus.zip "$(dirname "$0")/IN_udp6-h"
+zip -jqr $OUT/fuzz-tftp6_seed_corpus.zip "$(dirname "$0")/IN_tftp6"
+zip -jqr $OUT/fuzz-icmp6_seed_corpus.zip "$(dirname "$0")/IN_icmp6"
+zip -jqr $OUT/fuzz-tcp6_seed_corpus.zip "$(dirname "$0")/IN_tcp6"
+
+find $build -type f -executable -name "fuzz-*" -exec mv {} $OUT \;
+find $build -type f -name "*.options" -exec mv {} $OUT \;