Remove duplicate EXIT_RUNTIME flag (--emrun turns this flag on)

[mcbarton]

Description

Please include a summary of changes, motivation and context for this PR.

If you look at the description of emscriptens --emrun flag here https://emscripten.org/docs/tools_reference/emcc.html (search --emrun), you'll see that it enables EXIT_RUNTIME=1 . Therefore including it as a flag for the test executable is a duplication that can be removed.

Fixes # (issue)

Type of change

Please tick all options which are relevant.

• Bug fix
• New feature
• Added/removed dependencies
• Required documentation updates

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.78%. Comparing base (7a3a24b) to head (4144153).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #358   +/-   ##
=======================================
  Coverage   81.78%   81.78%           
=======================================
  Files          20       20           
  Lines         950      950           
  Branches       87       87           
=======================================
  Hits          777      777           
  Misses        173      173           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.