tree 05e878074a195464f479c0028f19198621b14ea9
parent 1e704462510e225716fbb8c5758fdd698bf7edb6
author Dan Willemsen <dwillemsen@google.com> 1474255661 -0700
committer Dan Willemsen <dwillemsen@google.com> 1486418707 -0800

Add microfactory to bootstrap a go program with minimal overhead

microfactory is a tool to incrementally compile a go program. It's
similar to `go install`, but doesn't require a GOPATH. A package->path
mapping can be specified as command line options. All input files are
hashed, and if any change, the necessary packages will be rebuilt.

microfactory can (re)build itself as necessary, so combined with a shell
script that runs `go run microfactory.go` the first time, it can
bootstrap a go program entirely from sources with just a working goroot.

Time to build soong_ui only using source & GOROOT:

            first time    no-change incremental
microfactory  1400ms               15ms
go install     670ms              130ms

While microfactory takes longer the first time, almost half of that time
is from `go run` and building microfactory for use later. If
microfactory only has to build soong_ui, it's about 580ms.

Test: USE_SOONG_UI=true m -j blueprint_tools
Test: go test -bench . build/soong/cmd/microfactory/microfactory_test.go
Change-Id: I4d2b9825788144fa10042bbd804482e44f459a54