Check LLVM_BUILD_LLVM_C_DYLIB before building the C DLL with MSVC

[aaron.ballman]

Summary

I think this may have been an oversight when the functionality originally landed, but it seems there is no other way to disable building the LLVM C bindings with MSVC without this change. I freely admit this is not my area of expertise though.

FWIW, I need this functionality because llvm-nm does not appear to work properly in Debug builds on Windows (executing gen-msvc-exports.py runs llvm-nm which fails because it doesn't understand any command line arguments due to crashing) and I needed a workaround to be able to build again.

[xbolva00]

Ok, makes sense.

[aaron.ballman]

Thanks! I've commit in 95eb50c4470894e4cebb08ba3ea97efe2f7c179a

llvm/tools/llvm-shlib/CMakeLists.txt

if(LLVM_BUILD_LLVM_C_DYLIB AND NOT MSVC)
   target_link_libraries(LLVM-C PUBLIC LLVM)
   add_dependencies(LLVM-C libLLVMCExports)
   
   set_property(TARGET LLVM-C APPEND_STRING PROPERTY
               LINK_FLAGS
               " -compatibility_version 1 -current_version ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH} -Wl,-reexport_library ${LIB_PATH}")
 endif()
 
-if(MSVC)
+if(LLVM_BUILD_LLVM_C_DYLIB AND MSVC)
   # Build the LLVM-C.dll library that exports the C API.
 
   set(LLVM_LINK_COMPONENTS
     ${LLVM_DYLIB_COMPONENTS}
     )
 
   llvm_map_components_to_libnames(LIB_NAMES ${LLVM_DYLIB_COMPONENTS})
   list(REMOVE_DUPLICATES LIB_NAMES)