[lld] [llvm] [hexagon] Bump the default version to v68 (PR #132304)

[Fangrui Song via llvm-commits]

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@@ -11,6 +11,9 @@
 # RUN: llvm-mc -triple=hexagon -mv75 -filetype=obj %s | llvm-readelf -h - | FileCheck --check-prefix=CHECK-V75 %s
 # RUN: llvm-mc -triple=hexagon -mv79 -filetype=obj %s | llvm-readelf -h - | FileCheck --check-prefix=CHECK-V79 %s
 
+# Check which arch version llvm-mc sets when the user does not provide one.
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MaskRay wrote:

`## ` (to make non-RUN non-CHECK comments stand out; help automation; etc)

https://github.com/llvm/llvm-project/pull/132304