install: don't output "additional options" when there are none.

nvm.sh

diff --git a/nvm.sh b/nvm.sh
index ed01e08..bbeba05 100644
--- a/nvm.sh
+++ b/nvm.sh
@@ -495,7 +495,9 @@
         fi
       fi
 
-      echo "Additional options while compiling: $ADDITIONAL_PARAMETERS"
+      if [ -n "$ADDITIONAL_PARAMETERS" ]; then
+        echo "Additional options while compiling: $ADDITIONAL_PARAMETERS"
+      fi
 
       tarball=''
       sum=''