cmdstanr::cmdstanr_example() (or any other via brms) fails to compile via github Actions

[pcinereus]

Describe the bug
I am trying to incorporate cmdstanr in a github actions workflow.
Parts of my workflow include:

      # install R
      - uses: r-lib/actions/setup-r@v2
        with:
          r-version: ${{ matrix.config.R }}

      - name: Repos
        run: |
          cat("\noptions(repos=c(stan='https://mc-stan.org/r-packages/',CRAN ='https://cloud.r-project.org'))\n", file = "~/.Rprofile", append = TRUE)
        shell: Rscript {0}
        
      ## Install R packages
      - name: install R packages
        uses: r-lib/actions/setup-r-dependencies@v2
        with:
          cache-version: 2
          packages: |
            stan-dev/cmdstanr
.....
      - name: Install CmdStan
          shell: Rscript {0}
          run: |
            cmdstanr::check_cmdstan_toolchain(fix = TRUE)
            cmdstanr::install_cmdstan(cores = parallel::detectCores())
            cmdstanr::cmdstanr_example()

The last line above was put in as a test to help track down an issue.

When I run this workflow, it runs without error. However, if I then install quarto and attempt to render a document:

    # install quarto
     - name: Install quarto
       uses: quarto-dev/quarto-actions/setup@v2
     - name: Change ImageMagick policy to allow pdf->png conversion.
       run: |
         sudo sed -i 's/^.*policy.*coder.*none.*PDF.*//' /etc/ImageMagick-6/policy.xml
      - name: Make tutorials
       run: |
         echo "library(quarto); quarto_render(\"index.qmd\")" | R --no-save --no-restore;

If that document includes an R chunk that includes cmdstanr::cmdstanr_example(), it fails with the following:

Error in `if (stancflags_local != "") ...`:
! the condition has length > 1
Backtrace:
 1. cmdstanr::cmdstanr_example()
 2. cmdstanr::cmdstan_model(tmp, force_recompile = force_recompile)
 3. CmdStanModel$new(...)
 4. cmdstanr (local) initialize(...)
 5. self$compile(...)

This error seems to be as a result of the call to cmdstanr:::get_cmdstan_flags("STANCFLAGS") returning a vector of strings when only a single string seems to be expected.
This what is returned:

[1] "make[2]:"                                        
[2] "Entering"                                        
[3] "directory"                                       
[4] "'/home/runner/.cmdstan/cmdstan-2.35.0'STANCFLAGS"
[5] "=make[2]:"                                       
[6] "Leaving"                                         
[7] "directory"                                       
[8] "'/home/runner/.cmdstan/cmdstan-2.35.0'"         

To Reproduce
See above

Expected behavior
The example model to be compiled

Operating system
Ubuntu via github actions

CmdStanR version number
2.35.0

Additional context
I realize that the above is not really a reproducible example, but I suspect that to some the issue might be very obvious. If not, I am happy to try to make a more minimum reproducible example