Fix fpm installation on openSUSE 15.4; switch to nfpm

fpm currently fails to install because the public_suffix gem dependency
requires Ruby 2.6, which openSUSE 15.4 doesn't provide. Because there have
been so many Ruby dependency issues with fpm in the past, switch to the fewer-
dependency nfpm, which also has better support for code signing if we want to
do that in the future.

builder/package.opensuse-154

@@ -1,7 +1,7 @@
 #!/bin/bash
 
-if [[ ! -d /tmp/output/opensuse-154 ]]; then
-  mkdir -p /tmp/output/opensuse-154
+if [[ ! -d /tmp/output/${OS_IDENTIFIER} ]]; then
+  mkdir -p "/tmp/output/${OS_IDENTIFIER}"
 fi
 
 # R 3.x requires PCRE1
@@ -39,49 +39,59 @@ if [ -d /opt/R/${R_VERSION} ]; then
 fi
 EOF
 
-fpm \
-  -s dir \
-  -t rpm \
-  -v 1 \
-  -n "R-${R_VERSION}" \
-  --vendor "RStudio, PBC" \
-  --url "http://www.r-project.org/" \
-  --description "GNU R statistical computation and graphics system" \
-  --maintainer "RStudio, PBC <https://github.com/rstudio/r-builds>" \
-  --license "GPLv2" \
-  --after-install /post-install.sh \
-  --after-remove /after-remove.sh \
-  -p /tmp/output/opensuse-154/ \
-  -d fontconfig \
-  -d gcc \
-  -d gcc-c++ \
-  -d gcc-fortran \
-  -d glibc-locale \
-  -d gzip \
-  -d icu.691-devel \
-  -d libbz2-devel \
-  -d libcairo2 \
-  -d libcurl-devel \
-  -d libfreetype6 \
-  -d libgomp1 \
-  -d libjpeg62 \
-  -d libopenblas_pthreads-devel \
-  -d libpango-1_0-0 \
-  -d libreadline7 \
-  -d libtiff5 \
-  -d make \
-  -d ${pcre_lib} \
-  -d tar \
-  -d tcl \
-  -d tk \
-  -d unzip \
-  -d which \
-  -d xorg-x11 \
-  -d xorg-x11-fonts-100dpi \
-  -d xorg-x11-fonts-75dpi \
-  -d xz-devel \
-  -d zip \
-  -d zlib-devel \
-  "/opt/R/${R_VERSION}"
+cat <<EOF > /tmp/nfpm.yml
+name: R-${R_VERSION}
+version: 1
+version_schema: none
+release: 1
+maintainer: RStudio, PBC <https://github.com/rstudio/r-builds>
+description: |
+  GNU R statistical computation and graphics system
+vendor: RStudio, PBC
+homepage: https://www.r-project.org
+license: GPLv2+
+depends:
+- fontconfig
+- gcc
+- gcc-c++
+- gcc-fortran
+- glibc-locale
+- gzip
+- icu.691-devel
+- libbz2-devel
+- libcairo2
+- libcurl-devel
+- libfreetype6
+- libgomp1
+- libjpeg62
+- libopenblas_pthreads-devel
+- libpango-1_0-0
+- libreadline7
+- libtiff5
+- make
+- ${pcre_lib}
+- tar
+- tcl
+- tk
+- unzip
+- which
+- xorg-x11
+- xorg-x11-fonts-100dpi
+- xorg-x11-fonts-75dpi
+- xz-devel
+- zip
+- zlib-devel
+contents:
+- src: /opt/R/${R_VERSION}
+  dst: /opt/R/${R_VERSION}
+scripts:
+  postinstall: /post-install.sh
+  postremove: /after-remove.sh
+EOF
 
-export PKG_FILE=$(ls /tmp/output/opensuse-154/R-${R_VERSION}*.rpm | head -1)
+nfpm package \
+  -f /tmp/nfpm.yml \
+  -p rpm \
+  -t "/tmp/output/${OS_IDENTIFIER}"
+
+export PKG_FILE=$(ls /tmp/output/${OS_IDENTIFIER}/R-${R_VERSION}*.rpm | head -1)