Replace fpm with nfpm for the newest platforms

fpm has had multiple Ruby gem dependency issues, and nfpm has better support
for code signing if we wanted to do that in the future. The rest of the
platforms may be migrated to nfpm later.

builder/Dockerfile.rhel-9

@@ -32,8 +32,6 @@ RUN dnf -y upgrade \
     pcre2-devel \
     readline-devel \
     rpm-build \
-    ruby \
-    ruby-devel \
     tcl-devel \
     tex \
     texinfo-tex \
@@ -53,7 +51,9 @@ RUN curl "https://awscli.amazonaws.com/awscli-exe-linux-x86_64.zip" -o "awscliv2
     ./aws/install && \
     rm -rf aws awscliv2.zip
 
-RUN gem install fpm
+RUN curl -LO https://github.com/goreleaser/nfpm/releases/download/v2.18.1/nfpm_amd64.rpm && \
+    dnf install -y nfpm_amd64.rpm && \
+    rm nfpm_amd64.rpm
 
 RUN chmod 0777 /opt