feat: remove C source code from the precompile gem

to reduce the size of the gem file. This probably will annoy people
who use local rdocs (because we also have to remove the C files from
the set of extra_rdoc_files), but let's wait and see whether people
complain.

Closes #2077.

rakelib/cross-ruby.rake

@@ -298,7 +298,7 @@ if java?
     jruby_home = RbConfig::CONFIG['prefix']
     jars = ["#{jruby_home}/lib/jruby.jar"] + FileList['lib/*.jar']
 
-    ext.gem_spec.files.reject! { |f| f =~ %r{^ext/nokogiri/} }
+    ext.gem_spec.files.reject! { |path| File.fnmatch?("ext/nokogiri/**", path) }
 
     ext.ext_dir = 'ext/java'
     ext.lib_dir = 'lib/nokogiri'
@@ -349,7 +349,9 @@ else
         Nokogiri is built with the packaged libraries: #{libs}.
       EOS
 
-      spec.files.reject! { |path| File.fnmatch?('ports/*', path) }
+      spec.extra_rdoc_files.reject! { |path| File.fnmatch?("ext/nokogiri/**", path) }
+      spec.files.reject! { |path| File.fnmatch?("ext/nokogiri/**", path) }
+      spec.files.reject! { |path| File.fnmatch?("ports/*", path) }
       spec.dependencies.reject! { |dep| dep.name=='mini_portile2' }
 
       # when pre-compiling a native gem, package all the C headers in lib/nokogiri/include:

scripts/test-gem-file-contents

@@ -152,7 +152,7 @@ describe File.basename(gemfile) do
     end
 
     it "does not contain ext/nokogiri" do
-      skip "until we fix https://github.com/sparklemotion/nokogiri/issues/2077"
+      # https://github.com/sparklemotion/nokogiri/issues/2077
       assert_empty(gemfile_contents.grep(%r{^ext/nokogiri/}))
     end