Fix GCC 13+ build error: blake2.h alignment constraints

[melvincarvalho]

Summary

• Fixes build failure with GCC 13+ due to stricter alignment enforcement
• Removes unnecessary ALIGN(64) from BLAKE2 state structures
• Moves #pragma pack(pop) to correct position

Problem

GCC 13 and later enforce stricter alignment rules. Building fails with:

blake2.h:101:5: error: size of array element is not a multiple of its alignment
  101 |     blake2s_state S[8][1];

The blake2s_state and blake2b_state structs were declared with ALIGN(64) but their sizes are not multiples of 64 bytes. When used in arrays inside #pragma pack(push, 1), GCC 13 rejects this.

Solution

1. Remove ALIGN(64) from blake2s_state and blake2b_state - not needed for the reference (non-SIMD) implementation
2. Move #pragma pack(pop) before the parallel state structures that contain arrays of these types

Testing

• Clean build succeeds with GCC 13.3.0 on Ubuntu 24.04
• Full blockchain sync verified working

Fixes #143

[Copilot]

Pull request overview

This PR fixes a GCC 13+ build failure caused by stricter alignment enforcement when using ALIGN(64) on structures inside #pragma pack(1) blocks.

Key changes:

• Removed unnecessary ALIGN(64) attributes from blake2s_state and blake2b_state structures
• Relocated #pragma pack(pop) before parallel state structure definitions to prevent alignment conflicts

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