sys/targets: fix freebsd/386 executor build on some hosts
sys/targets: fix freebsd/386 executor build on some hosts

Add -B/usr/lib32 to 386 build flags.
The story behind -B/usr/lib32 is not completely clear, but it helps in some cases.
For context see discussion in https://github.com/google/syzkaller/pull/1202

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