Merging r368078:

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r368078 | quantum | 2019-08-06 22:09:04 +0200 (Tue, 06 Aug 2019) | 18 lines

[WebAssembly] Fix null pointer in createInitTLSFunction

Summary:
`createSyntheticSymbols`, which creates `WasmSym::InitTLS`, is only called
when `!config->relocatable`, but this condition is not checked when calling
`createInitTLSFunction`.

This diff checks `!config->relocatable` before calling `createInitTLSFunction`.

Fixes https://github.com/emscripten-core/emscripten/issues/9155.

Reviewers: tlively, aheejin, kripken, sbc100

Subscribers: dschuff, jgravelle-google, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65785
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llvm-svn: 368137