Adds support for grpcio-tool to FindNanopb.cmake (#561)

Refer to #560

Co-authored-by: Alex Pacini <alex.pacini@metaboards.com>
diff --git a/extra/FindNanopb.cmake b/extra/FindNanopb.cmake
index ee7a6fc..e2823ec 100644
--- a/extra/FindNanopb.cmake
+++ b/extra/FindNanopb.cmake
@@ -346,6 +346,8 @@
     PATHS
     ${PROTOBUF_SRC_ROOT_FOLDER}/vsprojects/Release
     ${PROTOBUF_SRC_ROOT_FOLDER}/vsprojects/Debug
+    ${NANOPB_SRC_ROOT_FOLDER}/generator-bin
+    ${NANOPB_SRC_ROOT_FOLDER}/generator
 )
 mark_as_advanced(PROTOBUF_PROTOC_EXECUTABLE)