misra-docker-images: Export ECR var

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I89b6e88364a2325661acd2704bc22e21d6cb17aa
diff --git a/misra-docker-images/builders.sh b/misra-docker-images/builders.sh
index 5b6ad0a..232323d 100644
--- a/misra-docker-images/builders.sh
+++ b/misra-docker-images/builders.sh
@@ -14,7 +14,7 @@
 cd misra-dockerfiles
 
 aws configure list
-ECR=987685672616.dkr.ecr.us-east-1.amazonaws.com
+export ECR=987685672616.dkr.ecr.us-east-1.amazonaws.com
 # we are expecting private files to be kept in the dockerfiles/*
 # subdirs with a matching name for the image
 aws s3 cp --recursive s3://trustedfirmware-misra/dockerfiles/ ./misra-dockerfiles