CI: Fix GCC-style asm %= unique ID translation to LLVM ${:uid} (#5037)

GCC inline assembly uses %= to generate a unique ID for each asm
statement, useful for creating unique labels. The existing code
translated this to $= which is not valid LLVM inline asm syntax.

This changes the translation to use ${:uid} which is the correct
LLVM syntax for generating unique IDs.

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Co-authored-by: Dev VM <dev@ldc>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>