component/golang: make go1.4 shared

We'll use "go1.4-bootstrap-20171003.tar.gz, which contains the Go
1.4 source code plus accumulated fixes to keep the tools running on
newer operating systems." as described in
https://golang.org/doc/install/source#bootstrapFromSource

(this archive contains the "time: Skip TestParseInLocation test."
commit)

component/golang/buildout.cfg

@@ -12,8 +12,9 @@ parts = gowork
 
 [golang-common]
 recipe = slapos.recipe.cmmi
+shared = true
 configure-command = :
-location = ${buildout:parts-directory}/${:_buildout_section_name_}
+location = @@LOCATION@@
 make-binary =
 make-targets= cd src && ./all.bash && cp -alf .. ${:location}
 # some testdata files have an issue with slapos.extension.strip.
@@ -23,14 +24,11 @@ environment =
   GOROOT_FINAL=${:location}
   ${:environment-extra}
 
-[golang14-repository]
-<= git-repository
-repository = https://github.com/golang/go.git
-revision = go1.4.3-16-g4d5426a
-
 [golang14]
 <= golang-common
-path = ${golang14-repository:location}
+# https://golang.org/doc/install/source#bootstrapFromSource
+url = https://dl.google.com/go/go1.4-bootstrap-20171003.tar.gz
+md5sum = dbf727a4b0e365bf88d97cbfde590016
 environment-extra =
 make-targets= cd src && ./make.bash && cp -alf .. ${:location}