title: Error on the stan file compilation using R 3.6.0. and Win 10
body: <pre><code>Error in compileCode(f, code, language = language, verbose = verbose) : 
    Compilation ERROR, function(s)/method(s) not created! Error in .shlib_internal(commandArgs(TRUE)) : 
    C++14 standard requested but CXX14 is not defined
  Calls: &lt;Anonymous&gt; -&gt; .shlib_internal
  Execution halted
  In addition: Warning message:
  In system(cmd, intern = !verbose) :
    running command 'C:/PROGRA~1/R/R-36~1.0/bin/x64/R CMD SHLIB file1a1860a0379.cpp 2&gt; file1a1860a0379.cpp.err.txt' had status 1
  Error in sink(type = "output") : invalid connection
  </code></pre>
  
  <p>Some non-English page said that we can overcome by executing the following R script, but it did not work in my case:</p>
  
  <pre><code>dotR &lt;- file.path(Sys.getenv("HOME"), ".R")
  if (!file.exists(dotR)) 
    dir.create(dotR)
  M &lt;- file.path(dotR, "Makevars")
  if (!file.exists(M)) 
    file.create(M)
  cat("\nCXX14FLAGS=-O3 -Wno-unused-variable -Wno-unused-function",
      "CXX14 = g++ -std=c++1y",
      file = M, sep = "\n", append = TRUE)
  </code></pre>
  
  <p>The above R script is same as in the following page:</p>
  
  <p><a href="https://github.com/stan-dev/rstan/issues/569" rel="nofollow noreferrer">https://github.com/stan-dev/rstan/issues/569</a></p>
  
  <hr>
  
  <p>I tried to uninstall and install according to the following page, but the above error  occurred.</p>
  
  <p>Rstan installation:   <a href="https://github.com/stan-dev/rstan/wiki/RStan-Getting-Started" rel="nofollow noreferrer">https://github.com/stan-dev/rstan/wiki/RStan-Getting-Started</a> </p>
  
  <p>REF; <a href="https://github.com/stan-dev/stan/issues/1613" rel="nofollow noreferrer">https://github.com/stan-dev/stan/issues/1613</a></p>
  
  <p>ref: <a href="https://github.com/stan-dev/rstan/issues/633" rel="nofollow noreferrer">https://github.com/stan-dev/rstan/issues/633</a></p>