[clang-repl] Implement LoadDynamicLibrary for clang-repl wasm use cases (#133037)

**Currently we don't make use of the JIT for the wasm use cases so the
approach using the execution engine won't work in these cases.**

Rather if we use dlopen. We should be able to do the following
(demonstrating through a toy project)

1) Make use of LoadDynamicLibrary through the given implementation

```
extern "C" EMSCRIPTEN_KEEPALIVE int load_library(const char *name) {
  auto Err = Interp->LoadDynamicLibrary(name);
  if (Err) {
    llvm::logAllUnhandledErrors(std::move(Err), llvm::errs(), "load_library error: ");
    return -1;
  }
  return 0;
}
```
2) Add a button to call load_library once the library has been added in
our MEMFS (currently we have symengine built as a SIDE MODULE and we are
loading it)

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
index fa4c143..f8c8d0a 100644
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -18,6 +18,7 @@
 #include "llvm/Support/VirtualFileSystem.h"
 #ifdef __EMSCRIPTEN__
 #include "Wasm.h"
+#include <dlfcn.h>
 #endif // __EMSCRIPTEN__
 
 #include "clang/AST/ASTConsumer.h"
@@ -711,6 +712,14 @@ llvm::Error Interpreter::Undo(unsigned N) {
 }
 
 llvm::Error Interpreter::LoadDynamicLibrary(const char *name) {
+#ifdef __EMSCRIPTEN__
+  void *handle = dlopen(name, RTLD_NOW | RTLD_GLOBAL);
+  if (!handle) {
+    llvm::errs() << dlerror() << '\n';
+    return llvm::make_error<llvm::StringError>("Failed to load dynamic library",
+                                               llvm::inconvertibleErrorCode());
+  }
+#else
   auto EE = getExecutionEngine();
   if (!EE)
     return EE.takeError();
@@ -722,6 +731,7 @@ llvm::Error Interpreter::LoadDynamicLibrary(const char *name) {
     EE->getMainJITDylib().addGenerator(std::move(*DLSG));
   else
     return DLSG.takeError();
+#endif
 
   return llvm::Error::success();
 }