title: R not recognizing GSL library undefined references
body: <p>I am installing a package from github in R (link here: <a href="https://github.com/aliceyiwang/mvabund" rel="nofollow noreferrer">https://github.com/aliceyiwang/mvabund</a>), using devtools. I have installed Rtools, using the instructions for another package (here: <a href="https://cran.r-project.org/web/packages/dynr/vignettes/InstallationForUsers.pdf" rel="nofollow noreferrer">https://cran.r-project.org/web/packages/dynr/vignettes/InstallationForUsers.pdf</a>) and all the checks there indicate that GSL and RTools are installed properly.</p>
  
  <p>I've set the Windows system environment variables LIB_GSL (as <code>"C:/R/local323"</code>) and PATHS (as <code>"C:/RTools/bin/", "C:/RTools/mingw_64/bin", "C:/R/R-3.5.1/bin"</code>)</p>
  
  <p>I also run the following code in R before installing the package:</p>
  
  <pre><code>Sys.setenv("LIB_GSL" = "C:/R/local323")
  Sys.setenv(BINPREF = "C:/Rtools/mingw_$(WIN)/bin/")
  Sys.setenv(PATH = paste(Sys.getenv("PATH"), "C:/RTools/bin/",
                          "C:/RTools/mingw_64/bin", "C:/R/R-3.5.1/bin", sep = ";"))
  </code></pre>
  
  <p><strong>Question:</strong></p>
  
  <p>When I run:</p>
  
  <pre><code>devtools::install_github("aliceyiwang/mvabund")
  </code></pre>
  
  <p>The code initiates well and starts installing the package. There comes a point, however, when this happens:</p>
  
  <pre><code>[...excluded very long list of undefined references like that below...]
  summary.o:summary.cpp:(.text+0x194c): undefined reference to `gsl_vector_free'
      collect2.exe: error: ld returned 1 exit status
      no DLL was created
      ERROR: compilation failed for package 'mvabund'
      * removing 'C:/R/R-3.5.1/library/mvabund'
      In R CMD INSTALL
      Error in i.p(...) : 
        (converted from warning) installation of package ‘C:/Users/Joshua/AppData/Local/Temp/RtmpsPp5oY/file2154340c11f8/mvabund_4.0.tar.gz’ had non-zero exit status
  </code></pre>
  
  <p>My guess is that somewhere, some path to those functions has not been defined properly. What am I doing wrong? </p>
  
  <p>My session info is </p>
  
  <pre><code>&gt; sessionInfo()
  R version 3.5.1 (2018-07-02)
  Platform: x86_64-w64-mingw32/x64 (64-bit)
  Running under: Windows &gt;= 8 x64 (build 9200)
  
  Matrix products: default
  
  locale:
  [1] LC_COLLATE=English_Australia.1252  LC_CTYPE=English_Australia.1252    LC_MONETARY=English_Australia.1252
  [4] LC_NUMERIC=C                       LC_TIME=English_Australia.1252    
  
  attached base packages:
  [1] stats     graphics  grDevices utils     datasets  methods   base     
  
  other attached packages:
  [1] usethis_1.4.0  devtools_2.0.1
  
  loaded via a namespace (and not attached):
   [1] Rcpp_1.0.0        rstudioapi_0.8    magrittr_1.5      pkgload_1.0.2     R6_2.3.0          rlang_0.3.0.1    
   [7] tools_3.5.1       pkgbuild_1.0.2    sessioninfo_1.1.1 cli_1.0.1         withr_2.1.2       remotes_2.0.2    
  [13] yaml_2.2.0        assertthat_0.2.0  digest_0.6.18     rprojroot_1.3-2   crayon_1.3.4      processx_3.2.1   
  [19] callr_3.1.0       fs_1.2.6          ps_1.2.1          curl_3.2          testthat_2.0.1    memoise_1.1.0    
  [25] glue_1.3.0        compiler_3.5.1    desc_1.2.0        backports_1.1.2   prettyunits_1.0.2
  &gt; 
  </code></pre>