update Xtensor.R

Author: fbourgin

.github/workflows/osx.yml

@@ -51,7 +51,7 @@ jobs:
         echo "which tar"
         which tar
         export TAR="/usr/bin/tar"
-        R -e "library(devtools); install_github('xtensor-stack/Xtensor.R', configure.args = '--novendor')"
+        R -e "library(devtools); install_github('fbourgin/Xtensor.R', ref = 'update_xtensor_0.27', configure.args = '--novendor')"
 
     - name: print R HOME
       run: |