Makefile: don't change source files in default action
Makefile: don't change source files in default action

Default make action invokes 'go generate'. That's not necessary.
File produced by 'go generate' are checked in. Do it in presubmit instead.

Default make action reformats source files. This is bad for users who
do not actually work on source code, but just use syzkaller:
1. requires clang-format to be installed
2. can change some source files (if they were checked in unformatted)
Don't reformat in 'make', instead do it in presubmit.

Also don't invoke 'go install ./...' as it can install too much
(e.g. all tools). Install just minimally necessary packages.

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