Fix CSV timestamp output with multi-character delimiters

[Shubham-Padkonde]

Problem

With a multi-character CSV delimiter, pcm-iio removes only the final character from the timestamp prefix. For ||, the header contains Date||Time|||Socket; an empty delimiter instead truncates Time to Tim. The same timestamp helper is used for data rows.

Change

Remove the full trailing delimiter before combining the timestamp with the remaining columns. Add a public display-builder regression test covering comma, ||, :::, and empty delimiters.

Validation

• New regression fails on the original code for both multi-character delimiters and the empty delimiter.
• Built pcm-iio-utest with CMake and GCC 13; all 4 tests pass after the fix.
• git diff --check passes.

Prepared with Codex assistance.

[Copilot]

🟢 Approval recommended

The focused fix correctly handles all supported delimiter lengths and includes appropriate regression coverage.

Pull request overview

Fixes CSV timestamp formatting when delimiters contain multiple characters or are empty.

Changes:

• Removes the complete trailing delimiter from generated timestamps.
• Adds regression coverage for comma, multi-character, and empty delimiters.

File summaries

File	Description
src/pcm-iio-pmu.cpp	Removes the full delimiter suffix from timestamps.
tests/utests/pcm-iio-utest.cpp	Verifies correctly formatted CSV headers across delimiter variants.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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[rdementi]

thanks!