ffi dependency missing on Fedora

[steverep]

I'll preface this issue by saying I'm not new to Linux and package installation, but I am new to all things Ruby and Travis. So I'm not sure if this is actually a Fedora issue, Ruby Gem issue, or a Travis issue, but at least you can document the fix here and and forward along.

The installation instructions in the README do not work for Fedora 25 (and possibly others). Aside from the fact that yum should be changed to dnf, the Travis gem fails to install because there is a missing package. After a lot of trial and error, I determined this was rubygem-ffi. In other words, the prerequisites should be:

$ dnf install ruby ruby-devel rubygem-ffi

Without that extra package, trying to install the Travis gem fails to create the Makefile and the log file isn't very useful because it only complains about installing development tools.

[soulomoon]

+1

[dilowagner]

+1

[i-dorofeev]

The package redhat-rpm-config is also needed:

sudo dnf install redhat-rpm-config

Otherwise it fails to build gem native extensions:

current directory: /usr/local/share/gems/gems/json-2.1.0/ext/json/ext/generator                                                                                                                                 
make "DESTDIR="                                                                                                                                                                                                 
gcc -I. -I/usr/include -I/usr/include/ruby/backward -I/usr/include -I. -DJSON_GENERATOR    -fPIC -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -mtune=generic -fPIC -m64 -o generator.o -c generator.c                                                                
gcc: error: /usr/lib/rpm/redhat/redhat-hardened-cc1: No such file or directory                                                                                                                                  
make: *** [Makefile:243: generator.o] Error 1