sys/syz-extract: fix a deadlock
sys/syz-extract: fix a deadlock

The jobs channel needs to have capacity to hold all files from all arches
since they may all be queued to the channel at the same time.
The bug was introduced in 44a5ca633e
("pkg/ast, pkg/compiler: support per-file metadata").
Restore full channel capacity.

Fixes #3197

google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller