Resolve GNU ld scripts

[winterheart]

Resolve GNU ld scripts with additional checks for UNIX-like systems (fixes #17).

[vtjnash]

As I mentioned in the bug report, I don't really want to be creating a fiction here about the result of dlopen on this input, which the Debian maintainers already marked invalid in bugzilla. But maybe useful for the error message to still parse the file name as you are doing here and then dumping that file to stderr/stdout to still save the user a step?

Suggested change

	#if defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__ELF__)
	/* Try to resolve ld script references. */
	char *name;
	const char *e;
	if (err && *err == '/' && (e = strchr(err, ':'))) {
	name = malloc(e - err);
	strncpy(name, err, e - err);
	char *test = resolve_ldscript(name);
	if (test != NULL) {
	// Let's try again...
	lib = dlopen(test, RTLD_LAZY);
	free(test);
	}
	if (name != NULL)
	free(name);
	}
	}
	if (!lib) {
	#endif
	#ifndef _WIN32
	/* Try to resolve ld script references. */
	char *name;
	const char *e;
	if (err && *err == '/' && (e = strchr(err, ':'))) {
	name = malloc(e - err + 1);
	strncpy(name, err, e - err);
	name[e - err] = '\0';
	char *test = dump_utf8_file(name);
	free(name);
	}
	#endif

Where the function dump_utf8_file dumps the text of a file if it seems to consist of only printable text:

void dump_utf8_file(const char *name)
{
    FILE *fp = fopen(name, "r");
    fseek(fp);
    size_t nb = ftell(fp);
    void *c = malloc(ftell(fp) + 1);
    rewind(fp);
    if (fread(c, nb + 1, 1, fp) != nb || !feof(fp))
        return;
    if (!u8_isprint(c, nb))
        return;
    fputs("File contents appear to be text:\n\n", stdout)
    fputs(c, stdout);
    fclose(fp);
}

void u8_isprint(const char *c, size_t nb) { /* check that nb bytes of c are valid utf8 encoded isprint characters */ }