This duplicates building common blueprint go packages between minibp and
the primary builder, but drastically simplifies the first stage,
removing the need to check in a generated build.ninja.in.
Change-Id: I639a9637f1ed36d4210823ef276c0f7a064a83bd
From commit 38cef8ac3979da8e13037540981fe7aecc1e1fbe
Removes Go 1.7 from travis, since this depends on os.Executable
Change-Id: I58e2ae542621ffad66e9e145031091cb93ebb497