[abigen] solc downloads

[trajan0x]

Problem

Users on Apple Silicon Macs (M1/M2/M3) currently face issues with our Docker-based abigen tool due to AMD64 architecture incompatibility. While Rosetta 2 provides a workaround, it's not ideal and can cause performance overhead and occasional stability issues.

Proposed Solution

Implement a fallback mechanism that downloads solc binaries directly instead of relying on Docker containers:

1. First attempt to use Docker-based solution
2. If Docker fails or we detect Apple Silicon architecture:
   • Download appropriate solc binary from ethereum/solc-bin repository
   • Store in local cache (e.g., ~/.cache/solc/)
   • Use binary directly for compilation

Benefits

• Eliminates Rosetta dependency on Apple Silicon
• Potentially faster compilation (no Docker overhead)
• More reliable cross-platform support
• Simpler setup for new developers

Implementation Notes

• Use solc-bin as source for binaries
• Cache downloaded versions to avoid repeated downloads
• Verify checksums for security
• Support version selection similar to current Docker implementation

Related

• Current Rosetta workaround documentation: abigen README#note-on-macos-and-rosetta