Replace fpm with nFPM for all other platforms

builder/Dockerfile.opensuse-153

@@ -10,6 +10,7 @@ RUN zypper --non-interactive update
 RUN zypper --non-interactive --gpg-auto-import-keys -n install \
     bzip2 \
     cairo-devel \
+    curl \
     fdupes \
     gcc \
     gcc-c++ \
@@ -41,8 +42,6 @@ RUN zypper --non-interactive --gpg-auto-import-keys -n install \
     python-pip \
     readline-devel \
     rpm-build \
-    ruby \
-    ruby-devel \
     shadow \
     tcl-devel \
     texinfo \
@@ -71,9 +70,9 @@ RUN zypper --non-interactive --gpg-auto-import-keys -n install \
 
 RUN pip install awscli
 
-# Pin fpm to avoid git dependency in 1.12.0
-RUN gem install fpm:1.11.0 && \
-    ln -s /usr/bin/fpm.ruby2.5 /usr/local/bin/fpm
+RUN curl -LO https://github.com/goreleaser/nfpm/releases/download/v2.18.1/nfpm_amd64.rpm && \
+    zypper --non-interactive --no-gpg-checks install nfpm_amd64.rpm && \
+    rm nfpm_amd64.rpm
 
 RUN chmod 0777 /opt