Docker image not building

[dfalster]

Failing with installation of RccpEigen, which is required by rstan

Rscript -e 'dockertest::build()'

...
* installing *source* package ‘RcppEigen’ ...
** package ‘RcppEigen’ successfully unpacked and MD5 sums checked
** libs
g++ -I/usr/share/R/include -DNDEBUG   -I"/usr/local/lib/R/site-library/Rcpp/include"  -I../inst/include -fpic  -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -g  -c RcppEigen.cpp -o RcppEigen.o
g++ -I/usr/share/R/include -DNDEBUG   -I"/usr/local/lib/R/site-library/Rcpp/include"  -I../inst/include -fpic  -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -g  -c fastLm.cpp -o fastLm.o
g++ -shared -L/usr/lib/R/lib -Wl,-z,relro -o RcppEigen.so RcppEigen.o fastLm.o -llapack -lblas -lgfortran -lm -lquadmath -L/usr/lib/R/lib -lR
/usr/bin/ld: cannot find -lgfortran
collect2: error: ld returned 1 exit status
/usr/share/R/share/make/shlib.mk:6: recipe for target 'RcppEigen.so' failed
make: *** [RcppEigen.so] Error 1
ERROR: compilation failed for package ‘RcppEigen’
* removing ‘/usr/local/lib/R/site-library/RcppEigen’
Error in install.packages(pkgs = opt$PACKAGES, lib = opt$libloc, repos = opt$repos,  : 
  installation of package ‘RcppEigen’ had non-zero exit status
INFO[0145] The command [/bin/sh -c install2.r --error      devtools     inline     RcppEigen     RcppRedis] returned a non-zero code: 1 
Error in docker_build(path, dockerfile, info$tagname, use_cache) : 
  Error running docker
Calls: <Anonymous> -> docker_build
Execution halted