Bug 1388573 - Imply needs-sccache from toolchain dependencies. r=dustin

After bug 1388569 and bug 1388572, all jobs that have needs-sccache set
have a dependency on either linux64-sccache or win64-sccache, and
vice-versa. Which means they are now redundant, and one should imply the
other.

--HG--
extra : rebase_source : ae72f67ccf2da7ba645416b8be4d10687005d01a

taskcluster/ci/build/linux.yml

@@ -554,7 +554,6 @@ linux64-ccov/opt:
     index:
         product: firefox
         job-name: linux64-ccov-opt
-    needs-sccache: false
     treeherder:
         platform: linux64-ccov/opt
         symbol: tc(B)

taskcluster/ci/static-analysis/kind.yml

@@ -20,7 +20,6 @@ job-defaults:
         symbol: S
         kind: build
         tier: 1
-    needs-sccache: true
 
 jobs:
     linux64-st-an/debug:

taskcluster/ci/valgrind/kind.yml

@@ -30,7 +30,6 @@ jobs:
             max-run-time: 72000
             env:
                 TOOLTOOL_MANIFEST: "browser/config/tooltool-manifests/linux64/releng.manifest"
-        needs-sccache: true
         run:
             using: mozharness
             actions: [get-secrets build valgrind-test]

taskcluster/taskgraph/transforms/build.py

@@ -20,7 +20,6 @@ def set_defaults(config, jobs):
     for job in jobs:
         job['treeherder'].setdefault('kind', 'build')
         job['treeherder'].setdefault('tier', 1)
-        job.setdefault('needs-sccache', True)
         _, worker_os = worker_type_implementation(job['worker-type'])
         worker = job.setdefault('worker', {})
         if worker_os == "linux":

taskcluster/taskgraph/transforms/toolchain.py

@@ -80,6 +80,9 @@ def use_toolchains(config, jobs):
                                    t, f))
             filenames[f] = t
 
+            if t.endswith('-sccache'):
+                job['needs-sccache'] = True
+
         if toolchains:
             job.setdefault('dependencies', {}).update(
                 ('toolchain-%s' % t, 'toolchain-%s' % t)