Installing package from different sources gives different performance

Question

I have tried installing the RcppArmadillo package sparta (which is on CRAN) using three different methods.

1. install.packages("sparta")
2. devtools::install() (inside the package folder)
3. devtools::build() and then install.package("path_to_build_file, repos = NULL, type = "source")

I then benchmarked a specific function, marg, from the sparta package and it turned out that installing with 1) and 3) yielded same results whereas using 2) the runtime of marg was more than twice as slow. I't seems to me that for all three methods, the same compiler, g++ = -std=gnu11, was used.

I have no clue why this is happening; any suggestions?