Makefile: don't do go install
Makefile: don't do go install

We did it for caching purposes, but now
(1) go command caches everything anyway,
(2) we use custom tags and flags, so result
    of go install is not reused anyway.

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