Subzero: inconsistency in registered threads option for the CommandLine with external LLVM

Bug: b/173422055
Change-Id: I5d3bbbd7c89771c3f4a4b0900e36eea971171c0f
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/50428
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Tested-by: Nicolas Caramelli <caramelli.devel@gmail.com>
diff --git a/third_party/subzero/src/IceClFlags.def b/third_party/subzero/src/IceClFlags.def
index 615a815..30bde36 100644
--- a/third_party/subzero/src/IceClFlags.def
+++ b/third_party/subzero/src/IceClFlags.def
@@ -35,7 +35,7 @@
   X(IRFilename, std::string, release_opt_flag, cl::Positional,                 \
     cl::desc("IR File"), cl::init("-"))                                        \
                                                                                \
-  X(NumTranslationThreads, uint32_t, release_opt_flag, "threads",              \
+  X(NumTranslationThreads, uint32_t, release_opt_flag, "num_threads",          \
     cl::desc("Number of translation threads (0 for purely sequential)"),       \
     cl::init(2))                                                               \
                                                                                \