Rollup merge of #32734 - tromey:dwarf-5-DW_LANG_Rust, r=michaelwoerister
Rollup merge of #32734 - tromey:dwarf-5-DW_LANG_Rust, r=michaelwoerister

Use DWARF 5 value for DW_LANG_Rust

DWARF 5 has assigned a value for `DW_LANG_Rust`.  See [the relevant DWARF issue](http://www.dwarfstd.org/ShowIssue.php?issue=140129.1).  Although DWARF 5 is not yet released, it seems ok to use this value as both GCC and LLVM are already using other `DW_LANG_` constants assigned in this way.

GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust