rts: Provide _lock_file in symbol table on Windows
rts: Provide _lock_file in symbol table on Windows

Test Plan: Validate on Windows, ensure that linking works.

Reviewers: Phyx, austin, erikd, simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2817

shlevy/ghc,ezyang/ghc,sdiehl/ghc,olsner/ghc,ezyang/ghc,sdiehl/ghc,olsner/ghc,sdiehl/ghc,sdiehl/ghc,olsner/ghc,olsner/ghc,shlevy/ghc,olsner/ghc,olsner/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,olsner/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc