docker: use build context

- add .dockerignore
- copy build context to PW_ROOT

Bug: 216
Change-Id: Ie5066b360eb272fe3adf020163d437f9077e1ab0
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/14240
Reviewed-by: Rob Mohr <mohrr@google.com>
Commit-Queue: Johan Euphrosine <proppy@google.com>

.dockerignore

diff --git a/.dockerignore b/.dockerignore
new file mode 120000
index 0000000..3e4e48b
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1 @@
+.gitignore
\ No newline at end of file

docker/Dockerfile

diff --git a/docker/Dockerfile b/docker/Dockerfile
index cfa0d17..4493851 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -26,9 +26,9 @@
 ENV PW_ENVIRONMENT_ROOT /pigweed-cache/environment
 ENV PW_CIPD_PACKAGE_FILES "$PW_ROOT/pw_env_setup/py/pw_env_setup/cipd_setup/*.json"
 
+COPY . $PW_ROOT
 # --shell-file is required, but we're going to ignore it.
-RUN git clone https://pigweed.googlesource.com/pigweed/pigweed $PW_ROOT && \
-    $PW_ROOT/pw_env_setup/py/pw_env_setup/env_setup.py \
+RUN $PW_ROOT/pw_env_setup/py/pw_env_setup/env_setup.py \
     --shell-file $PW_ROOT/init.sh \
     --pw-root $PW_ROOT \
     --install-dir $PW_ENVIRONMENT_ROOT