title: Cloud Build w/ cloudbuild.yaml in nested folder - build fails
body: <p>I am experimnting in automating parts of a project that I'd ideally deploy and forget about. The project is comprised of an XML parser and a small Flask website. At the moment the folder structure looks like this:</p>
  
  <pre><code>.
  ├── init.sql
  └── parser
      ├── cloudbuild.yaml
      ├── cloud_func
      │   └── main.py
      ├── Dockerfile
      ├── feed_parse.py
      ├── get_so.py
      ├── requirements.txt
      └── utils.py
  </code></pre>
  
  <p>Now, I can correctly set up the trigger to look at <code>/parser/cloudbuild.yaml</code>, but building the image with the following command raises an error:</p>
  
  <pre><code>build . --build-arg "CLIENT_CERT=$CSQL_CERT CLIENT_KEY=$CSQL_KEY SERVER_CA=$CSQL_CA SERVER_PW=$CSQL_PW SERVER_HOST=$CSQL_IP" -t gcr.io/and-reporting/appengine/so-parser:latest
  </code></pre>
  
  <pre><code>BUILD
  Already have image (with digest): gcr.io/cloud-builders/docker
  unable to prepare context: unable to evaluate symlinks in Dockerfile path: lstat /workspace/Dockerfile: no such file or directory
  ERROR
  ERROR: build step 0 "gcr.io/cloud-builders/docker" failed: exit status 1
  </code></pre>
  
  <p>it looks to me that gcp has troubles locating my <code>Dockerfile</code> which is in the same folder <code>cloudbuild.yaml</code> is located.<br>
  What am I missing?</p>
  
  <p>For the sake of completeness, the Dockerfile looks like this:</p>
  
  <pre><code>FROM python:3.7-alpine
  
  RUN apk update \
    &amp;&amp; apk add gcc python3-dev musl-dev libffi-dev \
    &amp;&amp; apk del libressl-dev \
    &amp;&amp; apk add openssl-dev
  
  COPY requirements.txt /
  RUN pip install --upgrade pip
  RUN pip install --no-cache-dir -r requirements.txt
  
  ADD . /parser
  WORKDIR /parser/
  RUN mkdir -p certs
  
  # Set env variables from secrets 
  ARG CLIENT_CERT
  ENV CSQL_CERT=${CLIENT_CERT}
  
  ARG CLIENT_KEY
  ENV CSQL_KEY=${CLIENT_KEY}
  
  ARG SERVER_CA
  ENV CSQL_CA=${SERVER_CA}
  
  ARG SERVER_PW
  ENV CSQL_PW=${SERVER_PW}
  
  ARG SERVER_HOST
  ENV CSQL_IP=${SERVER_HOST}
  
  # Get ssl certs in files
  RUN echo $CLIENT_CERT &gt; ./certs/ssl_cert.pem \
    &amp;&amp; echo $CLIENT_KEY &gt; ./certs/ssl_key.pem \
    &amp;&amp; echo $SERVER_CA &gt; ./certs/ssl_ca.pem
  
  CMD python get_so.py
  </code></pre>
  
  <p><strong>edit</strong>: and the <code>cloudbuild.yaml</code> I'm using for the build</p>
  
  <pre><code>steps:
  
  # Building image
  - name: 'gcr.io/cloud-builders/docker'
    args: [
       'build',
       '-f',
       'Dockerfile',
       '--build-arg',
       'CLIENT_CERT=$$CSQL_CERT CLIENT_KEY=$$CSQL_KEY SERVER_CA=$$CSQL_CA SERVER_PW=$$CSQL_PW SERVER_HOST=$$CSQL_IP',
       '-t',
       'gcr.io/$PROJECT_ID/appengine/so-parser:latest',
       '.'
    ]
    secretEnv: ['CSQL_CERT', 'CSQL_KEY', 'CSQL_CA', 'CSQL_PW', 'CSQL_IP']     
  
  # Push Images       
  # - name: 'gcr.io/cloud-builders/docker'
  #   args: ['push', 'gcr.io/$PROJECT_ID/appengine/so-parser:latest']
  
  secrets:
  - kmsKeyName: projects/myproject/locations/global/keyRings/so-jobs/cryptoKeys/board
    secretEnv:
     CSQL_CERT: [base64 string] 
     CSQL_KEY: [base64 string] 
     CSQL_CA: [base64 string] 
     CSQL_PW: [base64 string] 
     CSQL_IP: [base64 string] 
  </code></pre>