HPCC-9024 Fix FindR.cmake when related to Rembed plugin

Added a second PATH_SUFIX for testing.

Signed-off-by: Philip Schwartz <philip.schwartz@lexisnexis.com>
Merge pull request #4167 from pschwartz/HPCC-9024-fix-findr.cmake

HPCC-9024 Fix FindR.cmake when related to Rembed plugin

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>