test: cover exact package tool invocation paths

cmd/w6l/main.c

@@ -9,6 +9,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/stat.h>
 
 /* `path` is acceptable iff it's either an archive ("!<arch>\n") or
  * an ELF file ("\x7fELF"). Distros often ship lib<name>.so as a GNU
@@ -128,10 +129,9 @@ main(int argc, char **argv)
 	}
 	int rc = l_emit_elf(&l, f, base, base + 0x1000 + entry->val);
 	fclose(f);
-	if (rc == 0) {
-		char cmd[1024];
-		snprintf(cmd, sizeof cmd, "chmod +x %s", out);
-		(void)system(cmd);
+	if (rc == 0 && chmod(out, 0755) != 0) {
+		fprintf(stderr, "w6l: cannot make %s executable\n", out);
+		rc = 1;
 	}
 	free(inputs);
 	return rc;