Fix memory leak in dyn_erl.c --realpath code path

[lawless-m]

The find_prog() function returns a strdup()'d string that must be freed by the caller. In the --realpath code path (line 365-373), the function returns early without freeing this allocated memory, causing ASAN to report a 57-byte leak during Erlang builds with AddressSanitizer enabled.

This leak prevents building Erlang/OTP with ASAN leak detection enabled, which is valuable for fuzzing and security research of Erlang applications with native C code.

In the normal execution path, this memory is correctly freed at line 403 with efree(abspath). This fix adds the same cleanup to the --realpath early return path.

Tested by building OTP 26.2.5.12 with CFLAGS="-fsanitize=address" and ASAN_OPTIONS="detect_leaks=1", which previously failed at this leak and now completes successfully.

[CLAassistant]

All committers have signed the CLA.

[github-actions[bot]]

CT Test Results

    3 files    135 suites   49m 51s ⏱️ 1 656 tests 1 599 ✅ 57 💤 0 ❌ 2 294 runs  2 218 ✅ 76 💤 0 ❌

Results for commit 72308bcd.

:recycle: This comment has been updated with latest results.

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// Erlang/OTP Github Action Bot

[jhogberg]

Merged, thanks for the PR!