#2216: Update build_vt_sample.sh to use external fmt when it's requested

Author: JacobDomagala

ci/build_vt_sample.sh

@@ -50,6 +50,7 @@ then
       -Dvt_trace_only="1" \
       -Dvt_build_examples="0" \
       -Dvt_build_tests="0" \
+      -Dvt_external_fmt="${VT_EXTERNAL_FMT:-0}" \
       -DCMAKE_CXX_STANDARD="${CMAKE_CXX_STANDARD:-17}" \
       -DCMAKE_EXPORT_COMPILE_COMMANDS=1 \
       -DCMAKE_BUILD_TYPE="${CMAKE_BUILD_TYPE:-Release}" \