Log Message:
(devel/R-callr) Updated 3.7.5 to 3.7.6

# callr 3.7.6

* If the `CALLR_NO_TEMP_DLLS=true` env var is set then callr does not
  copy the dll the client DLL files from, in the subprocess. By
  default callr copies the DLL file that drives the callr subprocess into
  a temporary directory and loads it from there (#273).