builders.sh: fix a couple of bugs

The initial version of the builders script had some bugs in it.

First, the s3 cp was creating another "misra-dockerfiles" subdirectory
and copying the down an extra level instead of overlaying them onto
the contents of the misra-dockerfils.git repo.  This could cause the
build to error out when of the files from S3 were referenced in the
Dockerfile.

Also, the "$image" variable includes the prefix "./" which makes it
unsuitable to use for the tagname, so let's create a tag variable
using the last item of the path only by running basename on it.

Change-Id: I559211cf5c370a9e1785efd3c59a3c79b64581e5
diff --git a/misra-docker-images/builders.sh b/misra-docker-images/builders.sh
index 0d69eed..bf31964 100644
--- a/misra-docker-images/builders.sh
+++ b/misra-docker-images/builders.sh
@@ -17,20 +17,21 @@
 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
-find ./misra-dockerfiles
+aws s3 cp --recursive s3://trustedfirmware-misra/dockerfiles/ .
+find .
 aws ecr get-login-password --region us-east-1|docker login --username AWS --password-stdin $ECR
 
 
 for image in ./*
 do
+    tag=$(basename $image)
     test -d $image  && test -f $image/build.sh && \
     (
         set -ex
-        echo "Building image: misra:${image}"
+        echo "Building image: misra:${tag}"
         cd $image
         ./build.sh
-        echo "Upoading image: misra:${image}"
-        docker push $ECR/misra:$image
+        echo "Upoading image: misra:${tag}"
+        docker push $ECR/misra:$tag
     )
 done