is there a way to install rstan on a Gentoo amd64 system? rstan depends on v8-r (https://cran.r-project.org/web/packages/V8/index.html), which depends on a v8 installation. I haven't found a working v8 ebuild, v8 failed to compile with didactic-duck ebuilds. I also tried nodejs, without success. Compiling v8 from source failed with "unsupported linux distro".
Thanks, Sven
UPDATE: as of the latest version of V8 you can use:
# For Linux: download libv8 during installation
Sys.setenv(DOWNLOAD_STATIC_LIBV8=1)
install.packages("V8")
This way, you can install the V8 package on any x64 Linux system, without separate system requirements. See also this post: https://ropensci.org/technotes/2020/11/12/installing-v8/
Original answer
The R package V8 simply needs libv8 headers and shared library. The best solution is to use the V8 engine from NodeJS, but this can only be done if NodeJS itself was built with the --shared option. I don't use Gentoo myself, but from the above I guess this is currently not the case.
You have to talk to the maintainer of the nodejs package in Gentoo, and ask them to enable shared libnode. Below some references about this from Fedora and Debian, that might get you started:
If you can't get this to work, you could also build libv8 yourself, but I have to warn you this is pretty painful because upstream changes their API and build system every few weeks.
Some working examples are: