message: doc: explain why passing -mlinker-version is required
diff: @@ -5,6 +5,9 @@ XCODE_BUILD_ID=11C505
  LD64_VERSION=530
  OSX_SDK=$(SDK_PATH)/Xcode-$(XCODE_VERSION)-$(XCODE_BUILD_ID)-extracted-SDK-with-libcxx-headers
  +
  +# When cross-compiling for Darwin using Clang, -mlinker-version must be passed to
  +# ensure that modern linker features are enabled.
  darwin_CC=clang -target $(host) -mmacosx-version-min=$(OSX_MIN_VERSION) --sysroot $(OSX_SDK) -mlinker-version=$(LD64_VERSION)
  darwin_CXX=clang++ -target $(host) -mmacosx-version-min=$(OSX_MIN_VERSION) --sysroot $(OSX_SDK) -stdlib=libc++ -mlinker-version=$(LD64_VERSION)
  