[llvm] build Blake3 source with LLVM_EXPORTS defined

Author: andrurogerz

llvm/lib/Support/BLAKE3/CMakeLists.txt

@@ -85,3 +85,9 @@ endif()
 add_library(LLVMSupportBlake3 OBJECT EXCLUDE_FROM_ALL ${LLVM_BLAKE3_FILES})
 set_target_properties(LLVMSupportBlake3 PROPERTIES FOLDER "LLVM/Libraries")
 llvm_update_compile_flags(LLVMSupportBlake3)
+if(LLVM_BUILD_LLVM_DYLIB OR BUILD_SHARED_LIBS)
+  # Since LLVMSupportBlake3 is not defined using llvm_add_library(), we must
+  # define LLVM_EXPORTS here so its public interface is annotated with
+  # __declspec(dllexport) when building as a DLL on Windows.
+  target_compile_definitions(LLVMSupportBlake3 PRIVATE LLVM_EXPORTS)
+endif()