[lld][WebAssembly] Use createGlobalVariable helper function. NFC.
[lld][WebAssembly] Use createGlobalVariable helper function. NFC.

Differential Revision: https://reviews.llvm.org/D65911

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@368325 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld