Dockerfile: fix default umask

Dockerfile

@@ -47,10 +47,9 @@ RUN apt-get update \
   && apt-get remove --purge -y software-properties-common \
   && apt-get autoremove --purge -y \
   && rm -rf /var/lib/apt/lists/* \
-  && sed -i -E '/^session optional\s+pam_umask\.so$/ s/$/ umask=0022/' /etc/pam.d/common-session \
-  && sed -i -E '/^session optional\s+pam_umask\.so$/ s/$/ umask=0022/' /etc/pam.d/common-session-noninteractive \
+  && sed -i -E 's/^(USERGROUPS_ENAB\s+)yes$/\1no/' /etc/login.defs \
   && localedef -i en_US -f UTF-8 en_US.UTF-8 \
-  && useradd -m -s /bin/bash linuxbrew \
+  && useradd --create-home --shell /bin/bash --user-group linuxbrew \
   && echo 'linuxbrew ALL=(ALL) NOPASSWD:ALL' >>/etc/sudoers \
   && su - linuxbrew -c 'mkdir ~/.linuxbrew'