packaging(rpm): add armv7l to build.sh (QEMU on manylinux)

[satwareAG-ironMike]

Context

Add armv7l to the RPM build for AlmaLinux/Rocky ARM and Fedora ARM.

Acceptance Criteria

• packaging/rpm/build.sh accepts --arch armv7l
• Build uses QEMU on manylinux ARM rootfs (or native ARM runner if available)
• .rpm produced: php-firebird-13.0.0-1.el8.armv7l.rpm
• Package installs and loads on armv7l container

Dependencies

• Bug: Segfault in large BLOB fetch after transaction commit (blob_stream_chunked_write) #12 (rpm build.sh)

Suggested Test Plan

1. Run build with --arch armv7l
2. Install on armv7l AlmaLinux 8 container (QEMU)
3. php -m | grep firebird — loaded