Convert line-endings in generated bash scripts. (#8056)

Fixes #8050

The underlying problem is that we can't control how people have
configured their line-endings when developing on Windows. Git, for
example, has an option to always checkout Windows line endings and
checkin Unix line endings. To account for folks wanting to build images
from Docker for Windows, we can protect them by passing anything we
write from the local repository through the utility "dos2unix" which is
so prevalent its even in Alpine Linux.

Dockerfile

@@ -57,7 +57,7 @@ RUN /bin/bash -c 'TMP_PKG_DIR=$(mktemp -d); \
     all_modules=`find $TMP_PKG_DIR -name "*.whl"`; \
     pip install --no-cache-dir $all_modules; \
     pip install --no-cache-dir --force-reinstall --upgrade azure-nspkg azure-mgmt-nspkg;' \
- && cat /azure-cli/az.completion > ~/.bashrc \
+ && cat /azure-cli/az.completion | dos2unix > ~/.bashrc \
  && runDeps="$( \
     scanelf --needed --nobanner --recursive /usr/local \
         | awk '{ gsub(/,/, "\nso:", $2); print "so:" $2 }' \
@@ -66,7 +66,8 @@ RUN /bin/bash -c 'TMP_PKG_DIR=$(mktemp -d); \
         | sort -u \
     )" \
  && apk add --virtual .rundeps $runDeps \
- && apk del .build-deps
+ && apk del .build-deps \
+ && cat /usr/local/bin/az | dos2unix > /usr/local/bin/az
 
 WORKDIR /