Revert "change UID to 1000"

This reverts commit b4bb2ba7.

Dockerfile

@@ -31,7 +31,7 @@ RUN apt-get update \
     && rm -rf /var/lib/apt/lists/*
 
 # gluon build fails when running as root
-RUN useradd -m -d /build -u 1000 -g 1000 -o build
+RUN useradd -m -d /build -u 100 -g 100 -o build
 USER build
 # workaround for fatal: detected dubious ownership in repository at '/builds/firmware/site-ffs'
 # https://gitlab.com/gitlab-org/gitlab-runner/-/issues/29022