Quarto books on subst drives (windows) give problem with figures from R code when rendering to html

Bug description

When placing a book project in a subst drive on windows, and rendering to html, a weird problem arises: figures resulting from R code will be generated, but figures are not shown in the browser subsequently, because the output is placed into a subdirectory directly under the main directory, instead under _book. This results in error messages like

ERROR: The filename, directory name, or volume label syntax is incorrect. (os error 123), stat 'Q:\qbook\_book\C:\quartosubst\qbook\index_files'

Steps to reproduce

Here is a batch file that reproduces the error (on my windows 11 computer):

c:
mkdir quartosubst
subst q: c:\quartosubst
q:
quarto create project book qbook --no-open

echo. >> qbook\index.qmd
echo ```{r} >> qbook\index.qmd
echo plot(1:4) >> qbook\index.qmd
echo ``` >> qbook\index.qmd

quarto render /qbook/ --to html

If the book is created in the real folder c:\quartosubst instead of q:, there are no problems.

Expected behavior

The rendered html book should show a fancy plot on the index page

Actual behavior

The link to the plot is broken, as directory index_files is placed in the parent directory of _book.

Your environment

Windows 11,
Same behaviour in all IDEs: RStudio, VS-code, terminal

Quarto check output

[>] Checking versions of quarto binary dependencies...
Pandoc version 3.1.1: OK
Dart Sass version 1.55.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
Version: 1.3.450

The same behaviour is observed with Quarto version 1.4.534