Fix all warnings found by clang analyzer as reported by ojab in issue 3.

bin/xbps-bin/check.c

@@ -254,7 +254,6 @@ xbps_check_pkg_integrity(const char *pkgname)
 			}
 			rv = xbps_check_is_installed_pkg_by_pattern(reqpkg);
 			if (rv <= 0) {
-				rv = ENOENT;
 				printf("%s: dependency not satisfied: %s\n",
 				    pkgname, reqpkg);
 			}

bin/xbps-bin/main.c

@@ -158,7 +158,7 @@ main(int argc, char **argv)
 	bool yes, purge, with_debug, force_rm_with_deps, recursive_rm;
 	bool show_download_pkglist_url = false;
 
-	i = c = flags = rv = 0;
+	flags = rv = 0;
 	yes = purge = force_rm_with_deps = recursive_rm = with_debug = false;
 
 	while ((c = getopt(argc, argv, "VcdDFfpRr:vy")) != -1) {

bin/xbps-dgraph/main.c

@@ -258,7 +258,6 @@ parse_array_in_pkg_dictionary(FILE *f, prop_dictionary_t plistd,
 
 		keyobj = prop_dictionary_get_keysym(plistd, dksym);
 		keyname = strip_dashes_from_key(tmpkeyname);
-		optnodetmp = "";
 		optnode = NULL;
 
 		fprintf(f, "	main -> %s [label=\"%s\"];\n",