AWS Codebuild running shell script - shell

Question

I have a .NetCore based Lambda Project, that I want to build with AWS CodeBuild.
I have a CodeCommit Repo for the source, and I am using a Lambda to trigger build whenever there is a commit to my master branch. I do not want to use CodePipeline.
I the code build I will be doing following -
Build
Package
Upload package to S3
Run some AWS CLI commands to update the lambda function
Now I have a couple of shell scripts that I want to execute as part of this, these scripts are working fine for me locally and that is the reason I want to use them with CodeBuild.
I am using a Ubuntu based .net core image from AWS for my build and nn my code build project, I have updated the build spec to do - chmod +x *.sh in pre_build and made other changes to my buildspec.yml as per this thread: https://forums.aws.amazon.com/thread.jspa?messageID=760031 and also looked at following blog post trying to do something similar - http://openbedrock.blogspot.in/2017/03/aws-codebuild-howto.html
This is one such script that I want to execute:
#!/bin/bash
set -e
ZIPFILENAME=""
usage()
{
echo "build and package lambda project"
echo "./build-package.sh "
echo "Get this help message : -h --help "
echo "Required Parameters: "
echo "--zip-filename=<ZIP_FILE_NAME>"
echo ""
}
if [ $# -eq 0 ]; then
usage
exit 1
fi
while [ "$1" != "" ]; do
PARAM=`echo $1 | awk -F= '{print $1}'`
VALUE=`echo $1 | awk -F= '{print $2}'`
case $PARAM in
-h | --help)
usage
exit
;;
--zip-filename)
ZIPFILENAME=$VALUE
;;
*)
echo "ERROR: unknown parameter \"$PARAM\""
usage
exit 1
;;
esac
shift
done
Now, I am getting error trying to execute shell command in Code Build:
Running command:
sh lambda-deployer.sh --existing-lambda=n --update-lambda=y
lamdbda-deployer.sh: 5: lambda-deployer.sh: Syntax error: "(" unexpected