Ignore vagrant files

CMakeLists.txt

@@ -505,7 +505,7 @@ if (FMT_MASTER_PROJECT AND EXISTS ${gitignore})
     string(REPLACE "*" ".*" line "${line}")
     set(ignored_files ${ignored_files} "${line}$" "${line}/")
   endforeach ()
-  set(ignored_files ${ignored_files} /.git /build)
+  set(ignored_files ${ignored_files} /.git /build .vagrant)
 
   set(CPACK_SOURCE_GENERATOR ZIP)
   set(CPACK_SOURCE_IGNORE_FILES ${ignored_files})