golang: Don't require users to put \ into gowork.install

Previously it was required to put \ into multi-entry gowork.install,
because the way it was processed was to directly pass it into bash
command, and if \n were there the command was cut by bash and the
trailing was considered as another command.

We can avoid that by explicitly processing \n in gowork.install and
translate it to just ' '. This helps people because now gowork.install
becomes just a regular multiline buildout entry, similar e.g. to
gowork.cpkgpath et all.

Here is one example where it helps:

jerome/slapos@95c45fe0 (comment 68408)

component/golang/buildout.cfg

@@ -61,8 +61,8 @@ environment-extra =
 #
 #   [gowork]
 #   install =
-#       lab.nexedi.com/kirr/neo/go/...  \
-#       github.com/pkg/profile          \
+#       lab.nexedi.com/kirr/neo/go/...
+#       github.com/pkg/profile
 #       golang.org/x/perf/cmd/benchstat
 #
 # For Cgo support pkg-config is made pre-available by gowork, and users
@@ -120,7 +120,7 @@ stop-on-error = true
 # clients should put package list to install to gowork:install ("..." requests installing everything)
 [gowork.goinstall]
 recipe  = plone.recipe.command
-command = bash -c ". ${gowork:env.sh} && go install ${gowork:buildflags} -v ${gowork:install}"
+command = bash -c ". ${gowork:env.sh} && go install ${gowork:buildflags} -v $$(echo -n '${gowork:install}' |tr '\n' ' ')"
 update-command = ${:command}
 stop-on-error = true
 

software/gitlab/software.cfg

@@ -191,9 +191,9 @@ environment =
 [gowork]
 golang  = ${golang19:location}
 install = 
-  lab.nexedi.com/kirr/git-backup \
-  gitlab.com/gitlab-org/gitlab-workhorse \
-  gitlab.com/gitlab-org/gitlab-workhorse/cmd/gitlab-zip-cat \
+  lab.nexedi.com/kirr/git-backup
+  gitlab.com/gitlab-org/gitlab-workhorse
+  gitlab.com/gitlab-org/gitlab-workhorse/cmd/gitlab-zip-cat
   gitlab.com/gitlab-org/gitlab-workhorse/cmd/gitlab-zip-metadata
 
 cpkgpath =

software/neotest/software.cfg

@@ -46,8 +46,8 @@ parts =
 # go packages to install (+ automatically their dependencies)
 [gowork]
 install =
-    lab.nexedi.com/kirr/neo/go/...  \
-    github.com/pkg/profile          \
+    lab.nexedi.com/kirr/neo/go/...
+    github.com/pkg/profile
     golang.org/x/perf/cmd/benchstat
 
 cpkgpath =