Add exec to node commands in the binary

[romandrahan]

Summary

After merging #1180 yarn binary executes node commands it these ways:

node "$basedir/yarn.js" "$@"
# and
nodejs "$basedir/yarn.js" "$@"

This leads to the fact, that yarn uses /bin/sh for running:

# ps aufx
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         8  0.0  0.0   4340   756 ?        S    08:08   0:00 /bin/sh /usr/local/bin/yarn test:unit
root        19  4.0  3.3 1083008 69008 ?       Sl   08:08   0:00  \_ node /opt/yarn/bin/yarn.js test:unit
root        29 28.6  7.4 1284500 152928 ?      Sl   08:08   0:06      \_ node /app/node_modules/.bin/karma start test/unit/karma.conf.js --single-run

It causes problems when Yarn is running in Docker container - it doesn't handle SIGTERM or any other signals.

To resolve this issue we can rewrite node commands to these:

exec node "$basedir/yarn.js" "$@"
# and
exec nodejs "$basedir/yarn.js" "$@"

With that, Yarn will be started directly without /bin/sh:

$ ps aufx
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  2.3  2.8 1070088 58524 ?       Ssl  08:56   0:00 node /usr/local/bin/yarn test:unit
root        14  0.0  0.0   4340   748 ?        S    08:56   0:00 sh -c karma start test/unit/karma.conf.js --single-run 
root        15 22.9  7.6 1286672 155688 ?      Sl   08:56   0:06  \_ node /app/node_modules/.bin/karma start test/unit/karma.conf.js --single-run

And SIGTERM became working.

Test plan

$ docker run node yarn test:unit
...
$ ^C
$ make: *** [test.unit] Error 130

[arcanis]

That seems better indeed, I just hope it won't have any unforeseen effect. Thanks!