Install flatbuffers from conda defaults (#22)

Summary:
Per the discussion with cccclai, we need to have flatbuffers installed from conda to have the `flatc` executable.  The current version (2.0.0) is newer than the required version used internally.

Pull Request resolved: #22

Reviewed By: cccclai

Differential Revision: D47768270

Pulled By: huydhn

fbshipit-source-id: 6d60a6aa343b4d0529456d2576854891378eea12

Author: huydhn

.ci/docker/common/install_conda.sh

@@ -27,7 +27,7 @@ install_miniconda() {
 install_python() {
   pushd /opt/conda
   # Install the correct Python version
-  as_ci_user conda create -n "py_${PYTHON_VERSION}" -y python="${PYTHON_VERSION}"
+  as_ci_user conda create -n "py_${PYTHON_VERSION}" -y --file /opt/conda/conda-env-ci.txt python="${PYTHON_VERSION}"
   popd
 }
 

.ci/docker/conda-env-ci.txt

@@ -0,0 +1,3 @@
+# TODO: We might need to update this to install flatbuffers from the pinned commit
+# in fbcode/executorch/third-party/flatbuffers.submodule.txt
+flatbuffers=2.0.0

.ci/docker/requirements-ci.txt

@@ -1,4 +1,3 @@
-flatbuffers==2.0
 mpmath==1.3.0
 PyYAML==6.0.1
 ruamel.yaml==0.17.32

.ci/docker/ubuntu/Dockerfile

@@ -29,9 +29,10 @@ ARG PYTHON_VERSION
 ENV PYTHON_VERSION=$PYTHON_VERSION
 ENV PATH /opt/conda/envs/py_$PYTHON_VERSION/bin:/opt/conda/bin:$PATH
 COPY requirements-ci.txt /opt/conda/
+COPY conda-env-ci.txt /opt/conda/
 COPY ./common/install_conda.sh install_conda.sh
 COPY ./common/utils.sh utils.sh
-RUN bash ./install_conda.sh && rm install_conda.sh utils.sh /opt/conda/requirements-ci.txt
+RUN bash ./install_conda.sh && rm install_conda.sh utils.sh /opt/conda/requirements-ci.txt /opt/conda/conda-env-ci.txt
 
 USER ci-user
 CMD ["bash"]