model-conversion : use BUILD_DIR variable in all scripts (#19015)

This commit modifies all the utility scripts to use an optional
BUILD_DIR variable/argument to specify the build directory.

The motivation for this is that Commit
3d55846a5c ("model-conversion : add
BUILD_DIR variable to run-converted-model scripts") introduced this
variable to the causal and embeddings scripts, but I missed the scripts
in the utils directory.

examples/model-conversion/scripts/utils/perplexity-gen.sh

@@ -3,6 +3,7 @@
 set -e
 
 CONVERTED_MODEL="${1:-"$CONVERTED_MODEL"}"
+BUILD_DIR="${2:-"$BUILD_DIR"}"
 
 # Final check if we have a model path
 if [ -z "$CONVERTED_MODEL" ]; then
@@ -25,9 +26,13 @@ mkdir -p ppl
 OUTPUTFILE="ppl/$(basename $CONVERTED_MODEL).kld"
 echo "Model: $CONVERTED_MODEL"
 
-cmake --build ../../build --target llama-perplexity -j8
+if [ -z "$BUILD_DIR" ]; then
+    BUILD_DIR="../../build"
+fi
 
-../.././build/bin/llama-perplexity -m $CONVERTED_MODEL \
+cmake --build $BUILD_DIR --target llama-perplexity -j8
+
+${BUILD_DIR}/bin/llama-perplexity -m $CONVERTED_MODEL \
     -f ppl/wikitext-2-raw/wiki.test.raw \
     --kl-divergence-base $OUTPUTFILE