`sam local invoke` fails due to file permissions made by `sam build`

### Description

`sam local invoke` fails due to `sam build` not providing all the needed file permissions for a successful mount into docker. Likely too many assumptions by `sam build` of umask, root, etc.

Fix is simple and discussed at https://superuser.com/questions/1482852/cant-get-aws-sam-hello-world-to-work-python/1483508

`sam` can not assume the permissions on the host filesystem are compatible with permissions needed inside the local docker test container. The uid and gid could be different. And the umask any permutation possible. Therefore `sam` must specifically set the permissions on these host filesystem files/dirs soon to be mounted into the docker container before mounting them.

### Setup

* Ubuntu 18.04.3 x86_64
* Python 3.7.3
* aws-cli/1.16.265 Python/3.6.8 Linux/5.0.0-32-generic botocore/1.13.1
* SAM CLI, version 0.23.0
* simple and valid template.yaml, requirements.txt, app.py, and myevent.json

### Steps to reproduce

1. `sam build --template template.yaml --manifest requirements.txt`
2. `sam local invoke --template .aws-sam/build/template.yaml --event myevent.json`

### Observed result

```
docker.errors.APIError: 400 Client Error: Bad Request ("OCI runtime create failed: container_linux.go:346: starting container process caused "chdir to cwd (\"/var/task\") set in config.json failed: permission denied": unknown")
```

### Expected result

No error. And the expected output of your app.py.

### Workaround

```bash
find .aws-sam/build/ -type d -print0 | xargs -0 chmod o+rx
find .aws-sam/build/ -type f -print0 | xargs -0 chmod o+r
```

### Debug output of `sam local invoke`

```
Using SAM Template at /mnt/**redacted**/**redacted**/**redacted**/**redacted**/.aws-sam/build/template.yaml
Telemetry endpoint configured to be https://aws-serverless-tools-telemetry.us-west-2.amazonaws.com/metrics
local invoke command is called
Collected default values for parameters: {'DNSZone': '**redacted**.com', 'LambdaVersionDescription': 'giterror-dirty'}
1 resources found in the template
Found Serverless function with name='**redacted**' and CodeUri='**redacted**'
Found one Lambda function with name '**redacted**'
Invoking app.lambda_handler (python3.7)
Environment variables overrides data is standard format
Loading AWS credentials from session with profile 'None'
2019-10-30 17:41:37 Found credentials in shared credentials file: ~/.aws/credentials
Resolving code path. Cwd=/mnt/**redacted**/**redacted**/**redacted**/**redacted**/.aws-sam/build, CodeUri=**redacted**
Resolved absolute path to code is /mnt/**redacted**/**redacted**/**redacted**/**redacted**/.aws-sam/build/**redacted**
Code /mnt/**redacted**/**redacted**/**redacted**/**redacted**/.aws-sam/build/**redacted** is not a zip/jar file
Skipping building an image since no layers were defined

Fetching lambci/lambda:python3.7 Docker container image......
Mounting /mnt/**redacted**/**redacted**/**redacted**/**redacted**/.aws-sam/build/**redacted** as /var/task:ro,delegated inside runtime container
Sending Telemetry: {'metrics': [{'commandRun': {'awsProfileProvided': False, 'debugFlagProvided': True, 'region': '', 'commandName': 'sam local invoke', 'duration': 3682, 'exitReason': 'APIError', 'exitCode': 255, 'requestId': '427ef3e7-a0a5-48a4-9413-dd724f3f9228', 'installationId': 'c648e689-e57c-4a3c-a26f-ca6d1fd13041', 'sessionId': 'c61bd142-b135-48e8-a771-1730684a3a0c', 'executionEnvironment': 'CLI', 'pyversion': '3.7.3', 'samcliVersion': '0.23.0'}}]}
HTTPSConnectionPool(host='aws-serverless-tools-telemetry.us-west-2.amazonaws.com', port=443): Read timed out. (read timeout=0.1)
Traceback (most recent call last):
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/docker/api/client.py", line 261, in _raise_for_status
response.raise_for_status()
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/requests/models.py", line 940, in raise_for_status
raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: http+docker://localhost/v1.35/containers/6134a91edcf955e40b2de58015590e2221dfa6c61180e2ae3826e2091c635226/start

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/bin/sam", line 8, in
sys.exit(cli())
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/decorators.py", line 64, in new_func
return ctx.invoke(f, obj, *args, **kwargs)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/lib/telemetry/metrics.py", line 93, in wrapped
raise exception # pylint: disable=raising-bad-type
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/lib/telemetry/metrics.py", line 62, in wrapped
return_value = func(*args, **kwargs)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/commands/local/invoke/cli.py", line 82, in cli
parameter_overrides,
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/commands/local/invoke/cli.py", line 151, in do_cli
context.function_name, event=event_data, stdout=context.stdout, stderr=context.stderr
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/commands/local/lib/local_lambda.py", line 97, in invoke
self.local_runtime.invoke(config, event, debug_context=self.debug_context, stdout=stdout, stderr=stderr)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/local/lambdafn/runtime.py", line 83, in invoke
self._container_manager.run(container)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/local/docker/manager.py", line 95, in run
container.start(input_data=input_data)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/samcli/local/docker/container.py", line 189, in start
real_container.start()
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/docker/models/containers.py", line 400, in start
return self.client.api.start(self.id, **kwargs)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/docker/utils/decorators.py", line 19, in wrapped
return f(self, resource_id, *args, **kwargs)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/docker/api/container.py", line 1095, in start
self._raise_for_status(res)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/docker/api/client.py", line 263, in _raise_for_status
raise create_api_error_from_http_exception(e)
File "/home/**redacted**/.local/share/virtualenvs/**redacted**-XSNsCDE1/lib/python3.7/site-packages/docker/errors.py", line 31, in create_api_error_from_http_exception
raise cls(e, response=response, explanation=explanation)
docker.errors.APIError: 400 Client Error: Bad Request ("OCI runtime create failed: container_linux.go:346: starting container process caused "chdir to cwd (\"/var/task\") set in config.json failed: permission denied": unknown")
```

### Related

https://github.com/awslabs/aws-sam-cli/issues/428