Multi addon projects (#413)

* Add --namespaced-targets to gyp-to-cmake

* Use namespaced targets in node-addon-examples

* Support building multiple addons

* Limit spawn concurrency

* Emit prebuilds per target, next to their sources

A project declaring multiple addons wrote every prebuild into a single
output directory, named after the CMake target. Both the location and the
name are now derived per target from the CMake File API:

- The output directory defaults to {targetSourceDir}/build/{configuration},
  where the new {targetSourceDir} placeholder expands to the target's own
  source directory. A single-addon project reports "." and so resolves to
  the same path as before.
- The prebuild is named after the artifact on disk (the target's
  OUTPUT_NAME) rather than the target name, so a target renamed to avoid a
  clash within the project still produces the name the JS require expects.

Together this keeps a prebuild where the Babel plugin and auto-linking
resolve it from, and reduces --namespaced-targets to an internal concern.

Also fixes, in the same area:

- gyp-to-cmake emitted OUTPUT_NAME regardless of --namespaced-targets, due
  to an always-truthy condition, and never emitted it for Apple framework
  targets, which CMake names after it.
- The Apple build ran a full "cmake --build" once per shared library,
  concurrently against one build tree, and called "xcodebuild -list" (a
  synchronous spawn) once per library per triplet.
- xcodebuild invocations now run in sequence per build directory, as
  concurrent invocations against a single Xcode project are not reliable.
- postBuild looked for "<target name>.framework" while createAppleFramework
  names it after the artifact, so the two diverged under namespacing.
- --concurrency accepted any value, and did not implement the documented
  fallback to 1 under --verbose. Max listeners is now derived from it.
- verify-prebuilds globbed a directory the prebuilds had moved out of, so
  it passed by finding nothing. It now covers tests/ too and requires a
  non-zero count.
- The root example project globbed recursively, which both missed examples
  copied in after configure and would add a nested project twice. It is
  now generated from the same script pipeline.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KfKQDvEkxNtkSE4aaF9yG8

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: kraenhansen

packages/node-addon-examples/tests/threadsafe-function/CMakeLists.txt

@@ -3,24 +3,26 @@ project(threadsafe-function-test)
 
 find_package(weak-node-api REQUIRED CONFIG)
 
-add_library(addon SHARED addon.c)
+add_library(threadsafe-function-test-addon SHARED addon.c)
 
 option(BUILD_APPLE_FRAMEWORK "Wrap addon in an Apple framework" ON)
 
 if(APPLE AND BUILD_APPLE_FRAMEWORK)
-  set_target_properties(addon PROPERTIES
+  set_target_properties(threadsafe-function-test-addon PROPERTIES
     FRAMEWORK TRUE
     MACOSX_FRAMEWORK_IDENTIFIER threadsafe-function-test.addon
     MACOSX_FRAMEWORK_SHORT_VERSION_STRING 1.0
     MACOSX_FRAMEWORK_BUNDLE_VERSION 1.0
     XCODE_ATTRIBUTE_SKIP_INSTALL NO
+    OUTPUT_NAME addon
    )
 else()
-  set_target_properties(addon PROPERTIES
+  set_target_properties(threadsafe-function-test-addon PROPERTIES
     PREFIX ""
     SUFFIX .node
+    OUTPUT_NAME addon
    )
 endif()
 
-target_link_libraries(addon PRIVATE weak-node-api)
-target_compile_features(addon PRIVATE cxx_std_17)
+target_link_libraries(threadsafe-function-test-addon PRIVATE weak-node-api)
+target_compile_features(threadsafe-function-test-addon PRIVATE cxx_std_17)