utils.sh: use commit hash for ESP-ADF

We currently point to the willow branch of our ESP-ADF fork. As long as
we don't update that branch, this is fine, but once this branch gets
updated, rebuilding Willow would result in a different binary, even when
building a tag. This makes bisecting near impossible.

Use a commit hash instead of a branch name to avoid above problems.

Dockerfile

@@ -27,7 +27,7 @@ COPY container.gitconfig /root/.gitconfig
 ENV PATH="$PATH:/willow/.local/bin"
 WORKDIR /willow
 
-ENV ADF_VER="willow"
+ENV ADF_VER="5cb9820cc1070e629d3439839f4449a61d3c53d6"
 RUN \
     cd /opt/esp/idf && \
     curl https://raw.githubusercontent.com/toverainc/esp-adf/$ADF_VER/idf_patches/idf_v4.4_freertos.patch | patch -p1