Bundled mksquashfs only supports zstd compression despite --comp parameter accepting other formats

[kem-a]

Issue: --comp parameter doesn't work with gzip/xz/lzo/lz4

Why other compression methods are not added?

Problem

Using --comp gzip fails because the bundled mksquashfs only supports zstd:

mksquashfs: Compressor "gzip" is not supported!
mksquashfs: Compressors available:
	zstd (default)

Cause

In ci/install-static-mksquashfs.sh, mksquashfs is built with only zstd enabled:

GZIP_SUPPORT=0 XZ_SUPPORT=0 LZO_SUPPORT=0 LZ4_SUPPORT=0 ZSTD_SUPPORT=1

Suggested Fix

Either:

• Enable all compression formats in the build script, OR
• Validate --comp parameter and reject unsupported formats with clear error message