Log Message:
erlang: Update to 21.2.4.

Changes:

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 --- erts-10.2.3 -----------------------------------------------------
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 Note! The erts-10.2.3 application can *not* be applied independently
       of other applications on an arbitrary OTP 21 installation.

       On a full OTP 21 installation, also the following runtime
       dependencies have to be satisfied:
       -- kernel-6.1 (first satisfied in OTP 21.1)
       -- sasl-3.3 (first satisfied in OTP 21.2)

 --- Fixed Bugs and Malfunctions ---

  OTP-15536    Application(s): erts
               Related Id(s): ERL-827

               Fix bug where doing a gen_tcp:send on a socket with
               delay_send set to true could cause a segfault if the
               other side closes the connection.

               Bug was introduced in erts-10.2 (OTP-21.2).

  OTP-15537    Application(s): erts

               Fix a race condition when a port program closes that
               could result in the next started port to hang during
               startup.

               When this fault happens the following error is normally
               (but not always) logged:

               =ERROR REPORT==== 14-Jan-2019::10:45:52.868246 ===
               Bad input fd in erts_poll()! fd=11, port=#Port<0.505>,
               driver=spawn, name=/bin/sh -s unix:cmd

               Bug was introduced in erts-10.0 (OTP-21.0).

  OTP-15538    Application(s): erts
               Related Id(s): ERIERL-229

               Fix a bug where polling for external events could be
               delayed for a very long time if all active schedulers
               were 100% loaded.

               Bug was introduced in erts-10.2 (OTP-21.2).

 Full runtime dependencies of erts-10.2.3: kernel-6.1, sasl-3.3,
 stdlib-3.5

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 --- inets-7.0.4 -----------------------------------------------------
 ---------------------------------------------------------------------

 The inets-7.0.4 application can be applied independently of other
 applications on a full OTP 21 installation.

 --- Fixed Bugs and Malfunctions ---

  OTP-15544    Application(s): inets
               Related Id(s): ERIERL-289

               Make sure ipv6 addresses with brackets in URIs are
               converted correctly before passing to lower level
               functions like gen_tcp and ssl functions. Could cause
               connection to fail.

 Full runtime dependencies of inets-7.0.4: erts-6.0, kernel-3.0,
 mnesia-4.12, runtime_tools-1.8.14, ssl-5.3.4, stdlib-3.5

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