pkg/kernel: skip test if gcc is not in PATH
pkg/kernel: skip test if gcc is not in PATH

gcc is not necessary available everywhere.
Skip the test instead of failing it.

google/syzkaller,hyz0906/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,dotweiba/syzkaller,hyz0906/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,dotweiba/syzkaller,google/syzkaller,zoulasc/syzkaller,xairy/syzkaller,hyz0906/syzkaller,xairy/syzkaller,zoulasc/syzkaller,dotweiba/syzkaller,zoulasc/syzkaller,xairy/syzkaller,hyz0906/syzkaller,xairy/syzkaller,hyz0906/syzkaller,google/syzkaller,xairy/syzkaller,zoulasc/syzkaller,dotweiba/syzkaller