merge.sh: Use "set -x".

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
diff --git a/coverage-tool/coverage-reporting/merge.sh b/coverage-tool/coverage-reporting/merge.sh
index 8304487..435a9d3 100755
--- a/coverage-tool/coverage-reporting/merge.sh
+++ b/coverage-tool/coverage-reporting/merge.sh
@@ -13,7 +13,7 @@
 # files.
 #==============================================================================
 
-set +x
+set -x
 #################################################################
 # Function to manipulate json objects.
 # The json object properties can be accessed through "." separated