Fix DBI loading problem on Linux (#82461)

src/coreclr/dlls/mscordbi/CMakeLists.txt

@@ -100,7 +100,21 @@ elseif(CLR_CMAKE_HOST_UNIX)
         mscordaccore
     )
 
-    target_link_libraries(mscordbi ${COREDBI_LIBRARIES})
+    # Before llvm 16, lld was setting `--undefined-version` by default. The default was
+    # flipped to `--no-undefined-version` in lld 16, so we will explicitly set it to
+    # `--undefined-version` for our use-case.
+    include(CheckLinkerFlag OPTIONAL)
+    if(COMMAND check_linker_flag)
+        check_linker_flag(CXX -Wl,--undefined-version LINKER_SUPPORTS_UNDEFINED_VERSION)
+        if (LINKER_SUPPORTS_UNDEFINED_VERSION)
+            add_linker_flag(-Wl,--undefined-version)
+        endif(LINKER_SUPPORTS_UNDEFINED_VERSION)
+    endif(COMMAND check_linker_flag)
+
+    # COREDBI_LIBRARIES is mentioned twice because ld is one pass linker and will not find symbols
+    # if they are defined after they are used. Having all libs twice makes sure that ld will actually
+    # find all symbols.
+    target_link_libraries(mscordbi ${COREDBI_LIBRARIES} ${COREDBI_LIBRARIES})
 
     add_dependencies(mscordbi mscordaccore)
 

src/coreclr/dlls/mscordbi/mscordbi.cpp

@@ -32,18 +32,3 @@ BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID lpReserved)
 	// Defer to the main debugging code.
     return DbgDllMain(hInstance, dwReason, lpReserved);
 }
-
-#if defined(HOST_LINUX) && defined(TARGET_LINUX)
-PALIMPORT HINSTANCE PALAPI DAC_PAL_RegisterModule(IN LPCSTR lpLibFileName);
-PALIMPORT VOID PALAPI DAC_PAL_UnregisterModule(IN HINSTANCE hInstance);
-
-HINSTANCE PALAPI PAL_RegisterModule(IN LPCSTR lpLibFileName)
-{
-     return DAC_PAL_RegisterModule(lpLibFileName);
-}
-
-VOID PALAPI PAL_UnregisterModule(IN HINSTANCE hInstance)
-{
-    DAC_PAL_UnregisterModule(hInstance);
-}
-#endif