Fix some unit tests for LLVM_ENABLE_EXPORTED_SYMBOLS_IN_EXECUTABLES=Off.

Building with -DLLVM_ENABLE_EXPORTED_SYMBOLS_IN_EXECUTABLES=Off should not
prevent the PluginsTests and DynamicLibraryTests unit tests from working.

This fix uses the approach implemented in
https://github.com/llvm/llvm-project/pull/101741.

rdar://135849875

llvm/unittests/Passes/Plugins/CMakeLists.txt

@@ -6,8 +6,9 @@ if (NOT WIN32 AND NOT CYGWIN)
   set(LLVM_LINK_COMPONENTS Support Passes Core AsmParser)
   add_llvm_unittest(PluginsTests
     PluginsTest.cpp
+
+    EXPORT_SYMBOLS
     )
-  export_executable_symbols_for_plugins(PluginsTests)
   target_link_libraries(PluginsTests PRIVATE LLVMTestingSupport)
 
   unset(LLVM_LINK_COMPONENTS)

llvm/unittests/Support/DynamicLibrary/CMakeLists.txt

@@ -17,9 +17,10 @@ set_output_directory(DynamicLibraryLib
 
 add_llvm_unittest(DynamicLibraryTests
   DynamicLibraryTest.cpp
+
+  EXPORT_SYMBOLS
   )
 target_link_libraries(DynamicLibraryTests PRIVATE DynamicLibraryLib)
-export_executable_symbols(DynamicLibraryTests)
 
 function(dynlib_add_module NAME)
   add_library(${NAME} MODULE