On Linux armhf i get with the same context and luatex:

mtx-context     | run 1: luatex --fmt="/usr/local/context/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luatex/cont-en" --jobname="witha" --lua="/usr/local/context/tex/texmf-cache/luatex-cache/context/5fe67e0bfe781ce0dde776fb1556f32e/formats/luatex/cont-en.lui" --no-parse-first-line --c:currentrun=1 --c:fulljobname="./witha.tex" --c:input="./witha.tex" --c:kindofrun=1 --c:maxnofruns=9 "cont-yes.mkiv"

This is LuaTeX, Version 1.09.0 (TeX Live 2018) 
 system commands enabled.
open source     > level 1, order 1, name '/usr/local/context/tex/texmf-context/tex/context/base/mkiv/cont-yes.mkiv'
system          > 
system          > ConTeXt  ver: 2018.06.22 15:55 MKIV beta  fmt: 2018.6.23  int: english/english
system          > 
system          > 'cont-new.mkiv' loaded
open source     > level 2, order 2, name '/usr/local/context/tex/texmf-context/tex/context/base/mkiv/cont-new.mkiv'
system          > beware: some patches loaded from cont-new.mkiv
close source    > level 2, order 2, name '/usr/local/context/tex/texmf-context/tex/context/base/mkiv/cont-new.mkiv'
system          > files > jobname 'witha', input './witha', result 'witha'
fonts           > latin modern fonts are not preloaded
languages       > language 'en' is active
open source     > level 2, order 3, name '/home/user/witha.tex'
fonts           > preloading latin modern fonts (second stage)
fonts           > 'fallback modern-designsize rm 12pt' is loaded
mtx-context     | fatal error: no return code, message: luatex: execution interrupted


No logfile is written.

a.tex
\starttext
\startMPpage
fill fullcircle scaled 5cm withcolor blue;
\stopMPpage
\stoptext

witha.tex
\starttext
\externalfigure[a.pdf]
\stoptext


Greetings Lutz

Am 23. Juni 2018 01:14:37 MESZ schrieb Akira Kakuto <kakuto@fuk.kindai.ac.jp>:
>> I get the same error after the update with 
>>
>> \starttext
>> \externalfigure[A]
>> \stoptext
>>
>> where A.pdf is in the current folder. I'm on windows 10.
>
>Here it works OK:
>
>LuaTeX, Version 1.09.0
>Development id: 6822
>
>Thanks,
>Akira
>
>___________________________________________________________________________________
>If your question is of interest to others as well, please add an entry
>to the Wiki!
>
>maillist : ntg-context@ntg.nl /
>http://www.ntg.nl/mailman/listinfo/ntg-context
>webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
>archive  : https://bitbucket.org/phg/context-mirror/commits/
>wiki     : http://contextgarden.net
>___________________________________________________________________________________