insert date into cgo files to invalidate cache

[sebastian-carpenter]

Modifying the underlying install of wolfssl may silently invalidate the binary go has cached for go-wolfssl.

For every package insert the date of options generation to help invalidate this cache. Updated README.md to reflect the new expectation of running generateOptions.sh with each modification of the wolfssl install.

[Copilot]

🟡 Changes recommended

README contains an invalid command placeholder and the generator uses a locale-dependent date string that can cause inconsistent generated output.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR adds an “options generation date” marker to cgo-bearing files and updates generateOptions.sh/README guidance so regenerating options can reliably invalidate Go’s build cache when the underlying wolfSSL install changes.

Changes:

• Add an // Options generation date: marker to the per-package cgo directive carriers.
• Update generateOptions.sh to write/update the date marker during option generation.
• Update README instructions to reflect the expectation of rerunning generateOptions.sh when the wolfSSL install is modified.

File summaries

File	Description
wolfx509/certgen_wolfcrypt.go	Adds options-generation date marker for wolfx509’s cgo directive carrier
wolftls/conn.go	Adds options-generation date marker for wolftls’ cgo directive carrier
aes.go	Adds options-generation date marker for wolfSSL package cgo directive carrier
examples/client/client-psk.go	Adds options-generation date marker to help invalidate cache for example build
examples/server/server-psk.go	Adds options-generation date marker to help invalidate cache for example build
generateOptions.sh	Writes the generation date into options.go and rewrites date markers across cgo files
README.md	Updates documentation to explain regeneration expectations and cache invalidation behavior

Review details

• Files reviewed: 7/7 changed files
• Comments generated: 2
• Review effort level: Lite

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[lealem47]

Thoughts on this approach?

  DATE="$(date -u +%Y%m%dT%H%M%SZ)"      # space-free, so it's a valid -D argument                                                                                    

  sed -i.bak \
      -e "s|^// #cgo CFLAGS:.*|// #cgo CFLAGS: -g -Wall -I$PREFIX/include -DGOWOLFSSL_STAMP=$DATE|" \                                                                 
      -e "s|^// #cgo LDFLAGS:.*|// #cgo LDFLAGS: -L$PREFIX/lib -lwolfssl -lm|" \
      $CGO_FILES
``