Only show log info when something has been logged

bin/ruby-build

@@ -28,13 +28,29 @@ build_failed() {
     echo "BUILD FAILED"
     echo
     echo "Inspect or clean up the working tree at ${TEMP_PATH}"
-    echo "Results logged to ${LOG_PATH}"
-    echo "Last 10 log lines:"
-    tail -n 10 $LOG_PATH
+
+    if file_is_not_empty "$LOG_PATH"; then
+      echo "Results logged to ${LOG_PATH}"
+      echo
+      echo "Last 10 log lines:"
+      tail -n 10 "$LOG_PATH"
+    fi
   } >&3
   exit 1
 }
 
+file_is_not_empty() {
+  local filename="$1"
+  local line_count="$(wc -l "$filename" 2>/dev/null || true)"
+
+  if [ -n "$line_count" ]; then
+    words=( $line_count )
+    [ "${words[0]}" -gt 0 ]
+  else
+    return 1
+  fi
+}
+
 install_package() {
   install_package_using "tarball" 1 $*
 }