• R: 4.1.2
• OS: ArchLinux
• g++: 11.2.0

Code should be placed in three backticks as shown below

* installing *source* package ‘mfa’ ...
** using staged installation
** libs
g++ -std=gnu++14 -I"/usr/include/R/" -DNDEBUG  -I'/usr/lib/R/library/Rcpp/include' -I/usr/local/include   -fpic  -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security         -fstack-clash-protection -fcf-protection -Wp,-D_GLIBCXX_ASSERTIONS -flto  -c RcppExports.cpp -o RcppExports.o
g++ -std=gnu++14 -I"/usr/include/R/" -DNDEBUG  -I'/usr/lib/R/library/Rcpp/include' -I/usr/local/include   -fpic  -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security         -fstack-clash-protection -fcf-protection -Wp,-D_GLIBCXX_ASSERTIONS -flto  -c gibbs.cpp -o gibbs.o
gibbs.cpp: In function ‘double log_d_norm(double, double, double)’:
gibbs.cpp:13:31: error: ‘PI’ was not declared in this scope
   13 |   double ldn = -0.5 * log(2 * PI);
      |                               ^~
make: *** [/usr/lib64/R/etc/Makeconf:177: gibbs.o] Error 1
make: *** Waiting for unfinished jobs....
ERROR: compilation failed for package ‘mfa’

http://bioconductor.org/checkResults/release/bioc-LATEST/mfa/nebbiolo2-install.html