fix test building for mac

diff --git a/icu4c/source/i18n/unitconverter.h b/icu4c/source/i18n/unitconverter.h
index b28aeedc0dc046f83d65fe5f1c0790ed5a45ed5d..738e1811c5176dff1be5118019f450ac2760f851 100644 (file)
--- a/icu4c/source/i18n/unitconverter.h
+++ b/icu4c/source/i18n/unitconverter.h
@@ -173,7 +173,7 @@ struct entry {
 /**
  * Converts from a source `MeasureUnit` to a target `MeasureUnit`.
  */
-class UnitConverter {
+class U_I18N_API UnitConverter {
   public:
     /**
      * Constructor of `UnitConverter`.