Bug 1460650 - Rename sixgill task name so it has "gcc" in it; r=nalexander

Mainly so searching "toolchain" + "gcc" yields something useful in the
taskgraph.

MozReview-Commit-ID: HWiT3AwwYQ2

--HG--
extra : rebase_source : b1ba0dfb4f99b6f8abe42506e8b37db68ed03590

taskcluster/ci/hazard/kind.yml

@@ -43,7 +43,7 @@ jobs:
         toolchains:
             - linux64-clang
             - linux64-gcc-6
-            - linux64-sixgill
+            - linux64-gcc-sixgill
             - linux64-rust
 
     linux64-haz/debug:
@@ -63,5 +63,5 @@ jobs:
         toolchains:
             - linux64-clang
             - linux64-gcc-6
-            - linux64-sixgill
+            - linux64-gcc-sixgill
             - linux64-rust

taskcluster/ci/toolchain/linux.yml

@@ -197,7 +197,7 @@ linux64-gcc-7:
             - 'build/unix/build-gcc/build-gcc.sh'
         toolchain-artifact: public/build/gcc.tar.xz
 
-linux64-sixgill:
+linux64-gcc-sixgill:
     description: "sixgill GCC plugin build"
     treeherder:
         kind: build