ci: Attempt to remove whitespace to fix sanitizer build (#2105)

Let's see if this does the trick. 
Alternatives are
- more complicated cleanup using sed or similar
- don't multiline the expression (e.g. "${{ multiline expression becomes
single line }}")
- don't wrap `SANITIZER_OPTION` in double quotes (like it was before)
- something else that i did not find - let me know if you know

.github/actions/generate/action.yml

@@ -73,7 +73,7 @@ runs:
       shell: bash
       env:
         BUILD_TYPE: "${{ inputs.build_type }}"
-        SANITIZER_OPTION: |
+        SANITIZER_OPTION: |-
           ${{ inputs.sanitizer == 'tsan' && '-Dsan=thread' ||
               inputs.sanitizer == 'ubsan' && '-Dsan=undefined' ||
               inputs.sanitizer == 'asan' && '-Dsan=address' ||