attempt to fix "build from source" for musl

Author: SamSaffron

.github/workflows/build.yml

@@ -358,7 +358,7 @@ jobs:
       - name: Set metadata
         id: set-metadata
         run: |
-            docker exec -w "${PWD}" ${{ steps.container.outputs.id }} ruby -e 'puts Gem.platforms.last.to_s' | tee gem_platform
+            docker exec -w "${PWD}" ${{ steps.container.outputs.id }} ruby -e 'p = Gem::Platform.local; parts = [p.cpu, p.os, p.version]; parts[2] = "musl" if RUBY_PLATFORM =~ /musl/; puts parts.compact.reject { |s| s.to_s.empty? }.join("-").gsub(/-darwin-?\d+/, "-darwin")' | tee gem_platform
             echo "GEM_PLATFORM=$(cat gem_platform)" >> $GITHUB_OUTPUT
       - name: Download a single artifact
         uses: actions/download-artifact@v4
@@ -473,7 +473,7 @@ jobs:
       - name: Set metadata
         id: set-metadata
         run: |
-            docker exec -w "${PWD}" ${{ steps.container.outputs.id }} ruby -e 'puts Gem::Platform.local.tap { |p| RUBY_PLATFORM =~ /musl/ && p.version.nil? and p.instance_eval { @version = "musl" } }.to_s' | tee gem_platform
+            docker exec -w "${PWD}" ${{ steps.container.outputs.id }} ruby -e 'p = Gem::Platform.local; parts = [p.cpu, p.os, p.version]; parts[2] = "musl" if RUBY_PLATFORM =~ /musl/; puts parts.compact.reject { |s| s.to_s.empty? }.join("-").gsub(/-darwin-?\d+/, "-darwin")' | tee gem_platform
             echo "GEM_PLATFORM=$(cat gem_platform)" >> $GITHUB_OUTPUT
       - name: Download a single artifact
         uses: actions/download-artifact@v4

ext/libv8-node/paths.rb

@@ -22,7 +22,17 @@ def object_paths
     end
 
     def platform
-      Gem::Platform.local.tap { |p| RUBY_PLATFORM =~ /musl/ && p.version.nil? && p.instance_eval { @version = 'musl' } }.to_s.gsub(/-darwin-?\d+/, '-darwin')
+      @platform ||= begin
+        local = Gem::Platform.local
+        parts = [local.cpu, local.os, local.version]
+        parts[2] = 'musl' if RUBY_PLATFORM =~ /musl/
+        ideal = parts.compact.reject { |s| s.to_s.empty? }.join('-').gsub(/-darwin-?\d+/, '-darwin')
+
+        return ideal if File.directory?(File.join(vendored_source_path, ideal))
+
+        available = Dir.glob(File.join(vendored_source_path, '*')).select { |d| File.directory?(d) }.map { |d| File.basename(d) } - ['include']
+        available.size == 1 ? available.first : ideal
+      end
     end
 
     def config

libexec/metadata

@@ -5,7 +5,7 @@ case "$1" in
         ruby -e 'puts RUBY_PLATFORM'
         ;;
     gem_platform)
-        ruby -e 'puts Gem::Platform.local.tap { |p| RUBY_PLATFORM =~ /musl/ && p.version.nil? and p.instance_eval { @version = "musl" } }.to_s.gsub(/-darwin-?\d+/, "-darwin")'
+        ruby -e 'p = Gem::Platform.local; parts = [p.cpu, p.os, p.version]; parts[2] = "musl" if RUBY_PLATFORM =~ /musl/; puts parts.compact.reject { |s| s.to_s.empty? }.join("-").gsub(/-darwin-?\d+/, "-darwin")'
         ;;
     gem_version|version)
         ruby -I'lib' -r'libv8/node/version' -e 'puts Libv8::Node::VERSION'