makefile: fix bug with testsys loglevel arg

[webern]

Issue #, if available:

Fixes #75

Description of changes:

The --log-level argument was being passed incorrectly to testsys. This fixes it.

Testing:

In Bottlerocket:

cargo make -e TWOLITER_VERSION=97937a81fcce104faaa2b7464936de8261bcd0a4 \
  -e TWOLITER_REPO=https://github.com/webern/twoliter \
  -e TWOLITER_SKIP_VERSION_CHECK=true \
  -e TWOLITER_ALLOW_BINARY_INSTALL=false \
  -e TWOLITER_LOG_LEVEL=trace \
  test --help

This was broken before but worked with these changes.

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