Correct silly type-o.  Thanks Richard.

llvm-svn: 176568
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 3fb6c6e50d4b3aaeed4fcd84579e3edfcc95423e
diff --git a/include/bitset b/include/bitset
index 06fd729..aa7a596 100644
--- a/include/bitset
+++ b/include/bitset
@@ -253,7 +253,7 @@
     : __first_{__v}
 #elif __SIZE_WIDTH__ == 32
     : __first_{__v, __v >> __bits_per_word}
-#elif
+#else
 #error This constructor has not been ported to this platform
 #endif
 #endif