Fix for bug #24611 "mysqld crashes when connecting from remote host, and compiled from source".

On some Linux distributions with both LinuxThreads and NPTL glibc versions available, statically built binaries can crash, because linker defaults to LinuxThreads when linking statically, but calls to external libraries (like libnss) are resolved to NPTL versions.

Since there is nothing we can do in the code to work that around, just give user an advice on how to fix that, if a crash happened on such a binary/OS combination.

sql/mysqld.cc

@@ -2146,6 +2146,16 @@ and configured to use LDAP in /etc/nsswitch.conf. You will need to either\n\
 upgrade to a version of glibc that does not have this problem (2.3.4 or\n\
 later when used with nscd), disable LDAP in your nsswitch.conf, or use a\n\
 mysqld that is not statically linked.\n");
+#endif
+
+#ifdef HAVE_NPTL
+  if (thd_lib_detected == THD_LIB_LT && !getenv("LD_ASSUME_KERNEL"))
+    fprintf(stderr,"\n\
+You are running a statically-linked LinuxThreads binary on an NPTL system.\n\
+This can result in crashes on some distributions due to LT/NPTL conflicts.\n\
+You should either build a dynamically-linked binary, or force LinuxThreads\n\
+to be used with the LD_ASSUME_KERNEL environment variable. Please consult\n\
+the documentation for your distribution on how to do that.\n");
 #endif
   
   if (locked_in_memory)