`LoadedLibraryPlugin` is currently just a wrapper of `void` pointer from
`dlopen`. This will be convenient for abstracting platform specific
dynamic linrary handling.
Make a single 'PluginRegistry' and share it between SwiftASTManager,
IDEInspectionInstance, and CompileInstance. And inject the plugin
registry to ASTContext right after 'CompilerInstance.setup()'
That way, all sema-capable ASTContext in SourceKit share a single
PluginRegistry.
When loading plugins from `-plugin-path`, use the global `PluginRegistry` to keep a record of what's loaded. Emit these dependencies to the loaded module trace.
Executable compiler plugins are programs invoked by the host compiler
and communicate with the host with IPC via standard IO (stdin/stdout.)
Each message is serialized in JSON, prefixed with a header which is a
64bit little-endian integer indicating the size of the message.
* Basic/ExecuteWithPipe: External program invocation. Lik
llvm::sys::ExecuteNoWait() but establishing pipes to the child's
stdin/stdout
* Basic/Sandbox: Sandboxed execution helper. Create command line
arguments to be executed in sandbox environment (similar to SwiftPM's
pluging sandbox)
* AST/PluginRepository: ASTContext independent plugin manager
* ASTGen/PluginHost: Communication with the plugin. Messages are
serialized by ASTGen/LLVMJSON
rdar://101508815
