A couple more tests for errexit involving subprocesses.

Didn't find any divergence in shell behavior.

spec/errexit.test.sh

@@ -211,7 +211,7 @@ echo 7
6
## END

### errexit double quard
### errexit double guard
# OSH bug fix.  ErrExit needs a counter, not a boolean.
set -o errexit
if { ! false; false; true; } then
@@ -223,3 +223,29 @@ echo done
## STDOUT:
true
## END

### background processes respect errexit
set -o errexit
{ echo one; false; echo two; exit 42; } &
wait $!
## status: 1
## STDOUT:
one
## END

### pipeline process respects errexit
set -o errexit
# It is respected here.
{ echo one; false; echo two; } | cat

# Also respected here.
{ echo three; echo four; } | while read line; do
  echo "[$line]"
  false
done
echo four
# status: 1
## STDOUT:
one
[three]
## END