[llvm] Initial changes for llvm shared library build using explicit visibility annotations (PR #96630)

[Petr Hosek via llvm-commits]

================
@@ -839,20 +841,36 @@ endif()
 
 if(MSVC)
   option(LLVM_BUILD_LLVM_C_DYLIB "Build LLVM-C.dll (Windows only)" ON)
-  # Set this variable to OFF here so it can't be set with a command-line
-  # argument.
-  set (LLVM_LINK_LLVM_DYLIB OFF)
   if (BUILD_SHARED_LIBS)
     message(FATAL_ERROR "BUILD_SHARED_LIBS options is not supported on Windows.")
   endif()
-else()
-  option(LLVM_LINK_LLVM_DYLIB "Link tools against the libllvm dynamic library" OFF)
+ else()
   option(LLVM_BUILD_LLVM_C_DYLIB "Build libllvm-c re-export library (Darwin only)" OFF)
-  set(LLVM_BUILD_LLVM_DYLIB_default OFF)
-  if(LLVM_LINK_LLVM_DYLIB OR LLVM_BUILD_LLVM_C_DYLIB)
-    set(LLVM_BUILD_LLVM_DYLIB_default ON)
-  endif()
-  option(LLVM_BUILD_LLVM_DYLIB "Build libllvm dynamic library" ${LLVM_BUILD_LLVM_DYLIB_default})
+endif()
+
+set(CAN_BUILD_LLVM_DYLIB Off)
+if(NOT MSVC OR LLVM_BUILD_LLVM_DYLIB_VIS)
+  set(CAN_BUILD_LLVM_DYLIB On)
+endif()
+
+CMAKE_DEPENDENT_OPTION(LLVM_LINK_LLVM_DYLIB "Link tools against the libllvm dynamic library" OFF
+                       "CAN_BUILD_LLVM_DYLIB" OFF)
+
+set(LLVM_BUILD_LLVM_DYLIB_default OFF)
+if(LLVM_LINK_LLVM_DYLIB OR LLVM_BUILD_LLVM_C_DYLIB)
+  set(LLVM_BUILD_LLVM_DYLIB_default ON)
+endif()
+CMAKE_DEPENDENT_OPTION(LLVM_BUILD_LLVM_DYLIB "Build libllvm dynamic library" ${LLVM_BUILD_LLVM_DYLIB_default}
+                       "CAN_BUILD_LLVM_DYLIB" OFF)
+
+CMAKE_DEPENDENT_OPTION(LLVM_DYLIB_EXPORT_INLINES "Force inline members of classes to be DLL exported when
+                       building with clang-cl so the libllvm DLL is compatible with MSVC"
+                       OFF
+                       "MSVC;LLVM_BUILD_LLVM_DYLIB_VIS" OFF)
----------------
petrhosek wrote:

We prefer lowercase spelling for CMake function.
```suggestion
cmake_dependent_option(LLVM_LINK_LLVM_DYLIB "Link tools against the libllvm dynamic library" OFF
                       "CAN_BUILD_LLVM_DYLIB" OFF)

set(LLVM_BUILD_LLVM_DYLIB_default OFF)
if(LLVM_LINK_LLVM_DYLIB OR LLVM_BUILD_LLVM_C_DYLIB)
  set(LLVM_BUILD_LLVM_DYLIB_default ON)
endif()
cmake_dependent_option(LLVM_BUILD_LLVM_DYLIB "Build libllvm dynamic library" ${LLVM_BUILD_LLVM_DYLIB_default}
                       "CAN_BUILD_LLVM_DYLIB" OFF)

cmake_dependent_option(LLVM_DYLIB_EXPORT_INLINES "Force inline members of classes to be DLL exported when
                       building with clang-cl so the libllvm DLL is compatible with MSVC"
                       OFF
                       "MSVC;LLVM_BUILD_LLVM_DYLIB_VIS" OFF)
```

https://github.com/llvm/llvm-project/pull/96630