fastrpc_test: DSP autolink, guarded timeout wrapper, and SKIP semantics for missing binary

[smuppand]

This PR addresses the enhancements that were requested as of now #179

Why

• On several images the DSP skeletons live under /usr/share/qcom/**/dsp but /usr/lib/dsp is empty. Manually creating SoC-specific links doesn’t scale and is brittle across new targets.
• Rootfs often lacks timeout/gtimeout, calling run_with_timeout with an empty/invalid timeout caused errors via functestlib.
• Tests should not fail when fastrpc_test isn’t installed yet or when /bin layout is disallowed by policy.

What changed (high level)

• Generic DSP autolink (idempotent, SoC-agnostic)
  • New ensure_usr_lib_dsp_symlinks() populates /usr/lib/dsp only if empty.
  • Auto-discovers the best source under /usr/share/qcom/**/dsp using detect_platform hints (if available), falling back to the most populated candidate.
  • Links both files and directories (e.g. adsp/, cdsp/), does not clobber existing names, and prints a short listing after completion.
  • Completely Yocto-safe (no sudo): requires root; optionally remounts the underlying FS rw if FASTRPC_AUTOREMOUNT=yes and restores ro unless FASTRPC_AUTOREMOUNT_RO=no.
  • Never hard-fails the testcase—warns and continues if linking isn’t possible.
• Guarded timeout wrapper
  • Introduced runWithTimeoutIfSet in run.sh to only call run_with_timeout when TIMEOUT is a positive integer and the function exists.
  • Otherwise executes the command directly. This fixes:
  • sleep: invalid number ''
• No dependency on external timeout/gtimeout binaries.
• SKIP semantics for absent binary / disallowed layout
  • If fastrpc_test is not present/executable at the chosen path, SKIP (emit fastrpc_test SKIP in .res) instead of FAIL.
  • If --bin-dir /bin is used and ALLOW_BIN_FASTRPC is not set, SKIP with a clear message (policy opt-in via ALLOW_BIN_FASTRPC=1).
• Minor quality-of-life
• --assets-dir is accepted for compatibility but logged as ignored under the new layout.
• Logging aligned with functestlib.sh.

Environment knobs

• FASTRPC_DSP_AUTOLINK=yes|no (default: yes) — enable/disable autolink.
• FASTRPC_DSP_SRC=/path/to/dsp — force a specific source directory.
• FASTRPC_AUTOREMOUNT=yes|no (default: no) — allow RO→RW remount to create /usr/lib/dsp and links.
• FASTRPC_AUTOREMOUNT_RO=yes|no (default: yes) — remount back to RO when we changed it.
• ALLOW_BIN_FASTRPC=1 — permit /bin/fastrpc_test usage when --bin-dir /bin.

User-visible behavior

• On first run where /usr/lib/dsp is empty:
• Auto-creates symlinks like: /usr/lib/dsp/adsp -> /usr/share/qcom////dsp/adsp /usr/lib/dsp/cdsp -> ...
• Logs how many links were created and lists them.
• If no source is found or filesystem is RO and remount not allowed → warns and continues (no FAIL).
• If fastrpc_test is missing → SKIP.
• If TIMEOUT unset or non-numeric → run without timeout (no wrapper errors).

[abbajaj806]

LGTM