Install Error - macOS Big Sur

Getting the error message below during installation. Any hints would be appreciated.

> Sys.setenv(DOWNLOAD_STATIC_LIBV8 = 1) # only necessary for Linux without the nodejs library / headers
> install.packages("rstan", repos = "https://cloud.r-project.org/", dependencies = TRUE)

  There is a binary version available but the source version is later:
      binary source needs_compilation
rstan 2.21.1 2.21.2              TRUE

Do you want to install from sources the package which needs compilation? (Yes/no/cancel) yes
installing the source package ‘rstan’

trying URL 'https://cloud.r-project.org/src/contrib/rstan_2.21.2.tar.gz'
Content type 'application/x-gzip' length 1152008 bytes (1.1 MB)
==================================================
downloaded 1.1 MB

* installing *source* package ‘rstan’ ...
** package ‘rstan’ successfully unpacked and MD5 sums checked
** using staged installation
** libs
clang++ -mmacosx-version-min=10.13 -std=gnu++14 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"../inst/include" -I"../inst/include/boost_not_in_BH" -I"." -DBOOST_DISABLE_ASSERTS -DBOOST_PHOENIX_NO_VARIADIC_EXPRESSION -DBOOST_NO_AUTO_PTR -D_REENTRANT -DSTAN_THREADS   -I'/Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include' -I'/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppEigen/include' -I'/Library/Frameworks/R.framework/Versions/4.0/Resources/library/BH/include' -I'/Library/Frameworks/R.framework/Versions/4.0/Resources/library/StanHeaders/include' -I'/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppParallel/include' -I/usr/local/include   -fPIC  -Wall -g -O2  -O3 -mtune=native -arch x86_64 -ftemplate-depth-256 -c Module.cpp -o Module.o
In file included from Module.cpp:1:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp.h:27:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/RcppCommon.h:29:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp/r/headers.h:67:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp/platform/compiler.h:100:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:317:9: error: no member named 'signbit' in the global namespace
using ::signbit;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:318:9: error: no member named 'fpclassify' in the global namespace
using ::fpclassify;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:319:9: error: no member named 'isfinite' in the global namespace; did you mean 'finite'?
using ::isfinite;
      ~~^
/usr/local/include/math.h:749:12: note: 'finite' declared here
extern int finite(double)
           ^
In file included from Module.cpp:1:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp.h:27:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/RcppCommon.h:29:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp/r/headers.h:67:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp/platform/compiler.h:100:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:320:9: error: no member named 'isinf' in the global namespace
using ::isinf;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:321:9: error: no member named 'isnan' in the global namespace
using ::isnan;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:322:9: error: no member named 'isnormal' in the global namespace
using ::isnormal;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:323:9: error: no member named 'isgreater' in the global namespace
using ::isgreater;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:324:9: error: no member named 'isgreaterequal' in the global namespace
using ::isgreaterequal;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:325:9: error: no member named 'isless' in the global namespace
using ::isless;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:326:9: error: no member named 'islessequal' in the global namespace
using ::islessequal;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:327:9: error: no member named 'islessgreater' in the global namespace
using ::islessgreater;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:328:9: error: no member named 'isunordered' in the global namespace
using ::isunordered;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:329:9: error: no member named 'isunordered' in the global namespace
using ::isunordered;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:335:9: error: no member named 'abs' in the global namespace; did you mean 'fabs'?
using ::abs;
      ~~^
/usr/local/include/math.h:417:15: note: 'fabs' declared here
extern double fabs(double);
              ^
In file included from Module.cpp:1:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp.h:27:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/RcppCommon.h:29:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp/r/headers.h:67:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include/Rcpp/platform/compiler.h:100:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:640:26: error: no template named 'numeric_limits'
    bool _FloatBigger = (numeric_limits<_FloatT>::digits > numeric_limits<_IntT>::digits),
                         ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:640:60: error: no template named 'numeric_limits'
    bool _FloatBigger = (numeric_limits<_FloatT>::digits > numeric_limits<_IntT>::digits),
                                                           ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:641:18: error: no template named 'numeric_limits'
    int _Bits = (numeric_limits<_IntT>::digits - numeric_limits<_FloatT>::digits)>
                 ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:641:50: error: no template named 'numeric_limits'
    int _Bits = (numeric_limits<_IntT>::digits - numeric_limits<_FloatT>::digits)>
                                                 ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:646:17: error: no template named 'numeric_limits'
  static_assert(numeric_limits<_FloatT>::radix == 2, "FloatT has incorrect radix");
                ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
make: *** [Module.o] Error 1
ERROR: compilation failed for package ‘rstan’
* removing ‘/Library/Frameworks/R.framework/Versions/4.0/Resources/library/rstan’

The downloaded source packages are in
	‘/private/var/folders/kw/_5nyl9vx5pn29m885dzd3hkm0000gn/T/RtmpH7j3f0/downloaded_packages’
Warning message:
In install.packages("rstan", repos = "https://cloud.r-project.org/",  :
  installation of package ‘rstan’ had non-zero exit status
> 

RStan Version:

R version 4.0.3 (2020-10-10)
Platform: x86_64-apple-darwin17.0 (64-bit)
Running under: macOS Big Sur 10.16

Matrix products: default
BLAS: /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRblas.dylib
LAPACK: /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRlapack.dylib

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

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

loaded via a namespace (and not attached):
[1] compiler_4.0.3 tools_4.0.3

The issue names no repository files, tests, or entry points; the available starting point is the reported rstan installation command and clang++ compiler trace. First determine whether the failure is project-side or specific to the macOS/Xcode environment. Done would require a reproducible project-side fix or documented resolution, but the issue does not define one.