Don't change directory for gem build.

This allows to continue to use `gem build ../foo.gemspec`.

https://github.com/rubygems/rubygems/issues/2587

ruby-2.6.0-No-chdir-for-build.patch

@@ -0,0 +1,95 @@
+From 5168efc9ba0a0644c4fd1dbe09c1799f71301e42 Mon Sep 17 00:00:00 2001
+From: Pavel Valena <pvalena@redhat.com>
+Date: Tue, 8 Jan 2019 14:51:46 +0100
+Subject: [PATCH] Revert 90e676886e681e16e34ef58e078bf0a0aae8b54f
+
+---
+ lib/rubygems/commands/build_command.rb        | 26 ++++++-------
+ .../test_gem_commands_build_command.rb        | 37 -------------------
+ 2 files changed, 12 insertions(+), 51 deletions(-)
+
+diff --git a/lib/rubygems/commands/build_command.rb b/lib/rubygems/commands/build_command.rb
+index e59471e976..3120236f9f 100644
+--- a/lib/rubygems/commands/build_command.rb
++++ b/lib/rubygems/commands/build_command.rb
+@@ -60,20 +60,18 @@ def execute
+     end
+ 
+     if File.exist? gemspec
+-      Dir.chdir(File.dirname(gemspec)) do
+-        spec = Gem::Specification.load File.basename(gemspec)
+-
+-        if spec
+-          Gem::Package.build(
+-            spec,
+-            options[:force],
+-            options[:strict],
+-            options[:output]
+-          )
+-        else
+-          alert_error "Error loading gemspec. Aborting."
+-          terminate_interaction 1
+-        end
++      spec = Gem::Specification.load gemspec
++
++      if spec
++        Gem::Package.build(
++          spec,
++          options[:force],
++          options[:strict],
++          options[:output]
++        )
++      else
++        alert_error "Error loading gemspec. Aborting."
++        terminate_interaction 1
+       end
+     else
+       alert_error "Gemspec file not found: #{gemspec}"
+diff --git a/test/rubygems/test_gem_commands_build_command.rb b/test/rubygems/test_gem_commands_build_command.rb
+index ac82a408c7..fa5e7454f3 100644
+--- a/test/rubygems/test_gem_commands_build_command.rb
++++ b/test/rubygems/test_gem_commands_build_command.rb
+@@ -192,43 +192,6 @@ def test_execute_missing_file
+     assert_equal "ERROR:  Gemspec file not found: some_gem\n", @ui.error
+   end
+ 
+-  def test_execute_outside_dir
+-    gemspec_dir = File.join @tempdir, 'build_command_gem'
+-    gemspec_file = File.join gemspec_dir, @gem.spec_name
+-    readme_file = File.join gemspec_dir, 'README.md'
+-
+-    FileUtils.mkdir_p gemspec_dir
+-
+-    File.open readme_file, 'w' do |f|
+-      f.write "My awesome gem"
+-    end
+-
+-    File.open gemspec_file, 'w' do |gs|
+-      gs.write @gem.to_ruby
+-    end
+-
+-    @cmd.options[:args] = [gemspec_file]
+-
+-    use_ui @ui do
+-      @cmd.execute
+-    end
+-
+-    output = @ui.output.split "\n"
+-    assert_equal "  Successfully built RubyGem", output.shift
+-    assert_equal "  Name: some_gem", output.shift
+-    assert_equal "  Version: 2", output.shift
+-    assert_equal "  File: some_gem-2.gem", output.shift
+-    assert_equal [], output
+-
+-    gem_file = File.join gemspec_dir, File.basename(@gem.cache_file)
+-    assert File.exist?(gem_file)
+-
+-    spec = Gem::Package.new(gem_file).spec
+-
+-    assert_equal "some_gem", spec.name
+-    assert_equal "this is a summary", spec.summary
+-  end
+-
+   def test_can_find_gemspecs_without_dot_gemspec
+     gemspec_file = File.join(@tempdir, @gem.spec_name)
+ 

ruby.spec

@@ -143,6 +143,10 @@ Patch9: ruby-2.3.1-Rely-on-ldd-to-detect-glibc.patch
 # Refresh expired certificates.
 # https://bugs.ruby-lang.org/issues/15502
 Patch10: ruby-2.6.0-Try-to-update-cert.patch
+# `gem build ../foo.gemspec` changes directory, which does not play well with
+# gems unpacked by setup macro.
+# https://github.com/rubygems/rubygems/issues/2587
+Patch11: ruby-2.6.0-No-chdir-for-build.patch
 
 # Add support for .include directive used by OpenSSL config files.
 # https://github.com/ruby/openssl/pull/216
@@ -561,6 +565,7 @@ rm -rf ext/fiddle/libffi*
 %patch7 -p1
 %patch9 -p1
 %patch10 -p1
+%patch11 -p1
 %patch22 -p1
 %patch23 -p1