Use system libraries for nokogiri

When running on ruby-head, nokogiri will need to compile itself.
However, it also needs to download external sources like iconv and zlib.
The mirrors it uses for that are pretty unreliable.

Author: Earlopain

.github/workflows/main.yml

@@ -111,6 +111,7 @@ jobs:
     env:
       PRISM_FFI_BACKEND: "true"
       BUNDLE_GEMFILE: gemfiles/${{ matrix.target.gemfile }}/Gemfile
+      NOKOGIRI_USE_SYSTEM_LIBRARIES: "true"
     steps:
       - uses: actions/checkout@v6
       - name: Set up Ruby
@@ -302,6 +303,7 @@ jobs:
           - { ruby: "jruby", os: "windows-latest", gemfile: ".." }
     env:
       BUNDLE_GEMFILE: gemfiles/${{ matrix.target.gemfile }}/Gemfile
+      NOKOGIRI_USE_SYSTEM_LIBRARIES: "true"
     runs-on: ${{ matrix.target.os }}
     steps:
     - uses: actions/checkout@v6