Add crasher check for passing a bad pthread_t to pthread_join.

Bug: http://b/35455349
Test: manual
Change-Id: If09454c7104a1e6de7c0edb50ee52118b7ca5eaa
diff --git a/debuggerd/crasher/crasher.cpp b/debuggerd/crasher/crasher.cpp
index cd45bbb..1c01e3e 100644
--- a/debuggerd/crasher/crasher.cpp
+++ b/debuggerd/crasher/crasher.cpp
@@ -189,6 +189,7 @@
     fprintf(stderr, "  fprintf-NULL          pass a null pointer to fprintf\n");
     fprintf(stderr, "  readdir-NULL          pass a null pointer to readdir\n");
     fprintf(stderr, "  strlen-NULL           pass a null pointer to strlen\n");
+    fprintf(stderr, "  pthread_join-NULL     pass a null pointer to pthread_join\n");
     fprintf(stderr, "\n");
     fprintf(stderr, "  no_new_privs          set PR_SET_NO_NEW_PRIVS and then abort\n");
     fprintf(stderr, "\n");
@@ -258,6 +259,8 @@
         readdir_null();
     } else if (!strcasecmp(arg, "strlen-NULL")) {
         return strlen_null();
+    } else if (!strcasecmp(arg, "pthread_join-NULL")) {
+        return pthread_join(0, nullptr);
     } else if (!strcasecmp(arg, "heap-usage")) {
         abuse_heap();
     } else if (!strcasecmp(arg, "SIGSEGV-unmapped")) {