R install on silicon Mac lacks long.double capability

On my new macbook pro, I installed R using package installer R-4.5.1-arm64.pkg
My installation lacks long.double and libxml capabilities.  How can these be enabled?

My installation was in two steps:
1.  Install Xcode developer tools (sudo xcode-select install), GNU fortran compiler (gfortran-14.2-universal.pkg at cran), gnu readline, liblzma, and pcre2 (using macports), texlive, and Xquartz.  Install R using above package installer.   
2.  Source install.R from https://mac.r-project.org/bin/.  In sudo R session, run install.libs("r-base-dev").  Reinstall R using above package installer.     

> capabilities()
       jpeg         png        tiff       tcltk         X11        aqua 
       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE 
   http/ftp     sockets      libxml        fifo      cledit       iconv 
       TRUE        TRUE       FALSE        TRUE        TRUE        TRUE 
        NLS       Rprof     profmem       cairo         ICU long.double 
       TRUE        TRUE        TRUE        TRUE        TRUE       FALSE 
    libcurl 
       TRUE 
> sessionInfo()
R version 4.5.1 (2025-06-13)
Platform: aarch64-apple-darwin20
Running under: macOS Sequoia 15.4.1

Matrix products: default
BLAS:   /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRblas.0.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.1

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: America/New_York
tzcode source: internal

attached base packages:
[1] stats     graphics  utils     datasets  grDevices methods   base     

other attached packages:
[1] latticeExtra_0.6-31 lattice_0.22-7      colorspace_2.1-2   

loaded via a namespace (and not attached):
[1] compiler_4.5.1     deldir_2.0-4       RColorBrewer_1.1-3 Rcpp_1.1.0        
[5] interp_1.1-6       jpeg_0.1-11        grid_4.5.1         png_0.1-8         
> 

nareshgurbuxani$ gfortran --version
GNU Fortran (GCC) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.