[SYCL][Driver][NFC] Make clang help a bit prettier (#4097)

Add a space and a full stop.

Author: Fznamznon

clang/include/clang/Driver/Options.td

@@ -2577,7 +2577,7 @@ def fsycl_link_targets_EQ : CommaJoined<["-"], "fsycl-link-targets=">, Flags<[No
   HelpText<"Specify comma-separated list of triples SYCL offloading targets to produce linked device images">;
 def fsycl_device_code_split_EQ : Joined<["-"], "fsycl-device-code-split=">,
    Flags<[CC1Option, CoreOption]>, HelpText<"Perform SYCL device code split: per_kernel (device code module is "
-  "created for each SYCL kernel) | per_source (device code module is created for each source (translation unit)) | off (no device code split). | auto (use heuristic to select the best way of splitting device code)"
+  "created for each SYCL kernel) | per_source (device code module is created for each source (translation unit)) | off (no device code split). | auto (use heuristic to select the best way of splitting device code). "
   "Default is 'auto' - use heuristic to distribute device code across modules">, Values<"per_source, per_kernel, off, auto">;
 def fsycl_device_code_split : Flag<["-"], "fsycl-device-code-split">, Alias<fsycl_device_code_split_EQ>,
   AliasArgs<["auto"]>, Flags<[CC1Option, CoreOption]>,