tools/oss-fuzz.sh doesn't seem to be working on systems where libFuzzer is a builtin sanitizer

[evverx]

$ ./tools/oss-fuzz.sh
+ export LC_CTYPE=C.UTF-8
+ LC_CTYPE=C.UTF-8

Appending LDFLAGS from environment: '-L/usr/lib64/clang/6.0.1/lib/linux'
Native C++ compiler: clang++ (clang 6.0.1 "clang version 6.0.1 (tags/RELEASE_601/final)")

meson.build:299:8: ERROR:  C++ library 'Fuzzer' not found

I think it would make sense to try compiling something like

#include <stddef.h>
#include <stdint.h>

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
	return 0;
}

with -fsanitize=fuzzer to check whether clang is new enough to support that.

That's not critical as long as libFuzzer is built as a static library by the OSS-Fuzz project for, I presume, backwards compatibility, but it would certainly make the script a little bit more useful for people who, for some reason, want to build the fuzzers without the Docker machinery.

[evverx]

Judging by google/oss-fuzz#2312 (comment), libFuzzingEngine.a will be removed in the future so it seems we'll have to support -fsanitize=fuzzer sooner or later.