[DWARF][NFC] Refactor range list emission to use a static helper
[DWARF][NFC] Refactor range list emission to use a static helper

This is prep for DWARF v5 range list emission. Emission of a single range list is moved
to a static helper function.

Reviewer: jdevlieghere

Differential Revision: https://reviews.llvm.org/D49098


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@336621 91177308-0d34-0410-b5e6-96231b3b80d8

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