ICU-21026 fix GCC warnings of signed-int left shift
diff --git a/icu4c/source/tools/gensprep/store.c b/icu4c/source/tools/gensprep/store.c
index 3d75a39..4b00d1b 100644
--- a/icu4c/source/tools/gensprep/store.c
+++ b/icu4c/source/tools/gensprep/store.c
@@ -412,7 +412,8 @@
         int16_t delta = (int16_t)((int32_t)codepoint - (int16_t) mapping[0]);
         if(delta >= SPREP_DELTA_RANGE_NEGATIVE_LIMIT && delta <= SPREP_DELTA_RANGE_POSITIVE_LIMIT){
 
-            trieWord = delta << 2;
+            trieWord = delta;
+            trieWord <<= 2;
 
 
             /* make sure that the second bit is OFF */