Make switch-to-latest-clang less verbose and other small fixes.

fpm/Dockerfile-ubuntu2004

 		ca-certificates \
 		libffi-dev \
 		ruby-ffi \
+		rpm \
+		vim \
 	&& gem install fpm \
 	&& mkdir /src/
 

fpm/Makefile

 	docker build . -f Dockerfile-ubuntu1804 -t rayburgemeestre/fpm-ubuntu:18.04
 
 ubuntu2004fpm:
-	docker pull rayburgemeestre/fpm-ubuntu:18.04 || true
+	docker pull rayburgemeestre/fpm-ubuntu:20.04 || true
 	docker build . -f Dockerfile-ubuntu2004 -t rayburgemeestre/fpm-ubuntu:20.04
 
 publish1804:

switch-to-latest-clang

 #!/bin/bash
 
-set -ex
-
+# set -ex
 update-alternatives --install /usr/bin/c++ c++ /usr/bin/clang++-12 40
 update-alternatives --install /usr/bin/cc cc /usr/bin/clang-12 40
 update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-12 40