Improve output of toolchain requirements test, workaround heisenbug ...

There is currently an Heisenbug in Github CI where dub fails to run the program.
E.g. we see the following in the logs:
---
Performing "debug" build using ldc2 for x86_64.
dubtest1531 ~master: building configuration "application"...
Linking...
Running ../../../../../tmp/dubtest1531_2enU78/dubtest1531
Failed to execute program (No such file or directory)
[ERROR] -e:79 Did not pass with ldc="<=1.23.0"
[ERROR] Script failure.
---
This works around said bug by only building the package,
but not running it.

Testsuite: Fix calls to die to always include line numbers ...

'die' actually taking two parameters seems to be a little-known fact.

Remove the additional '|' syntax for toolchain requirements. ...

- '|' seems confusing, given that it is used as a logical AND
- Dependency already supports specifying an arbitrary range and this is the only meaningful use for '|'
- Keeps the possibility open to use '|' as a logical OR in a later version
- Rewords the change log entry and adds a link to the DUB documentation

toolchainRequirements recipe support