#macOS MojaveでNokogiriがインストールできない問題解消のメモ
##概要
macOSのアップデート後から、Nokogiri Gemのインストールが痛恨の失敗！！
初心者の私には正直理解不能だったが頑張ってエラーを見てググる、を繰り返してみた。
##発生したエラー
" clang -o conftest -I/Users/user_name/.rbenv/versions/2.6.2/include/ruby-2.6.0/x86_64-darwin17
-I/Users/user_name/.rbenv/versions/2.6.2/include/ruby-2.6.0/ruby/backward
-I/Users/user_name/.rbenv/versions/2.6.2/include/ruby-2.6.0
-I. -I/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxslt/1.1.33/include
-I/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9/include/libxml2
-I/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9/include/libxml2
-I/Users/user_name/.rbenv/versions/2.6.2/include
-D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT "-DNOKOGIRI_LIBXML2_PATH=\"/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9\""
"-DNOKOGIRI_LIBXML2_PATCHES=\"0001-Revert-Do-not-URI-escape-in-server-side-includes.patch 0002-Remove-script-macro-support.patch 0003-Update-entities-to-remove-handling-of-ssi.patch\""
"-DNOKOGIRI_LIBXSLT_PATH=\"/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxslt/1.1.33\"" "-DNOKOGIRI_LIBXSLT_PATCHES=\"\"" -O3 -Wno-error=shorten-64-to-32 -pipe
-I /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/libxml2 -DNOKOGIRI_USE_PACKAGED_LIBRARIES conftest.c
-L. -L/Users/user_name/.rbenv/versions/2.6.2/lib -L/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9/lib -L/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxslt/1.1.33/lib
-L/usr/local/Cellar/xz/5.2.4/lib
-L. -L/Users/user_name/.rbenv/versions/2.6.2/lib
-fstack-protector-strong -L/usr/local/lib/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxslt/1.1.33/lib/libexslt.a
-lm -liconv -lpthread -llzma -lz /Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9/lib/libxml2.a/Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxslt/1.1.33/lib/libxslt.a
-lm -liconv -lpthread -llzma -lz /Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9/lib/libxml2.a
-llzma -lruby.2.6-static -framework Security -framework Foundation -lpthread -ldl -lobjc /Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxslt/1.1.33/lib/libexslt.a -lm -liconv -lpthread
-llzma -lz /Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9/lib/libxml2.a /Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxslt/1.1.33/lib/libxslt.a -lm -liconv -lpthread
-llzma -lz /Users/user_name/Desktop/app/app/vendor/bundler/ruby/2.6.0/gems/nokogiri-1.10.2/ports/x86_64-apple-darwin17.7.0/libxml2/2.9.9/lib/libxml2.a -llzma "
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: /*top*/
4: extern int t(void);
5: int main(int argc, char **argv)
6: {
7: if (argc > 1000000) {
8: int (* volatile tp)(void)=(int (*)(void))&t;
9: printf("%d", (*tp)());
10: }
11:
12: return 0;
13: }
14: extern void xmlSchemaSetParserStructuredErrors();
15: int t(void) { xmlSchemaSetParserStructuredErrors(); return 0; }
/* end */
##解決方法
bundle configでビルド時のオプションとして、--use-system-librariesと--with-xml2-includeを設定しておくといいらしい！
$ bundle config build.nokogiri --use-system-libraries --with-xml2-include=$(brew --prefix libxml2)/include/libxml2
###解決しました！
##参考
An error occurred while installing nokogiri (1.10.0), and Bundler cannot continue.