Add 7z archive support to MinArch

[nchapman]

Feature Request

Add support for 7z-compressed ROM files in MinArch (the libretro frontend).

Current Behavior

MinArch currently only supports ZIP archives via custom parsing in minarch_zip.c:

• Parses ZIP file headers manually
• Extracts using zlib (deflate compression only)
• Supports compression methods: 0 (store) and 8 (deflate)

Files with .7z extension are passed directly to cores, which typically cannot load them, resulting in black screens.

Desired Behavior

Support .7z archives the same way .zip archives are handled:

• Detect .7z extension
• Extract first matching ROM file from archive
• Pass extracted file to core

Implementation Options

Option 1: Shell out to 7z binary

• Bundle 7z binary for all platforms (Info-ZIP unzip already bundled for some)
• Call via system() to extract to /tmp/
• Simpler, handles both zip and 7z
• Downside: Process overhead for extraction

Option 2: Link against p7zip library

• Add LZMA decompression support to minarch_zip.c
• Native extraction like current ZIP handling
• More efficient, no process spawn
• Downside: Binary size increase, library dependency

Related Files

• workspace/all/minarch/minarch.c (line 215) - ZIP detection
• workspace/all/minarch/minarch_zip.c - ZIP extraction
• Existing unzip binaries: workspace/*/other/unzip60/unzip

Benefits

• Better compatibility with ROM sets that use 7z compression
• 7z typically achieves better compression than ZIP for ROMs
• Reduces user confusion about supported formats