[CMake] Fix DynamicLibraryTests exports symbol when plugins are enabled (#102941)

Exporting symbols from tools directory never worked with
`LLVM_EXPORT_SYMBOLS_FOR_PLUGINS=On`. When that options is on, only
symbols from the static library is linked is exported due to the export
symbols computation script. DynamicLibraryTests needs to export a symbol
from the tools/executable directory, so update it to use export list
instead.

Author: cachemeifyoucan

llvm/cmake/modules/AddLLVM.cmake

@@ -1071,7 +1071,7 @@ macro(add_llvm_executable name)
 
   if (DEFINED LLVM_ENABLE_EXPORTED_SYMBOLS_IN_EXECUTABLES AND
       NOT LLVM_ENABLE_EXPORTED_SYMBOLS_IN_EXECUTABLES AND
-      NOT ARG_EXPORT_SYMBOLS AND NOT ARG_EXPORT_SYMBOLS_FOR_PLUGINS)
+      NOT ARG_EXPORT_SYMBOLS)
     if(LLVM_LINKER_SUPPORTS_NO_EXPORTED_SYMBOLS)
       set_property(TARGET ${name} APPEND_STRING PROPERTY
         LINK_FLAGS " -Wl,-no_exported_symbols")

llvm/unittests/Support/DynamicLibrary/CMakeLists.txt

@@ -15,13 +15,17 @@ set_output_directory(DynamicLibraryLib
   LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}
   )
 
+set(LLVM_EXPORTED_SYMBOL_FILE ${CMAKE_CURRENT_SOURCE_DIR}/DynamicLibraryTests.exports)
+
 add_llvm_unittest(DynamicLibraryTests
   DynamicLibraryTest.cpp
 
   EXPORT_SYMBOLS
   )
 target_link_libraries(DynamicLibraryTests PRIVATE DynamicLibraryLib)
 
+unset(LLVM_EXPORTED_SYMBOL_FILE)
+
 function(dynlib_add_module NAME)
   add_library(${NAME} MODULE
     PipSqueak.cpp

llvm/unittests/Support/DynamicLibrary/DynamicLibraryTests.exports

@@ -0,0 +1 @@
+TestA