refactor: only run build pipeline in build environment

Since build env is setup for building images, it makes more sense to
have all build jobs in that environment.

.gitlab-ci.yml

@@ -113,7 +113,7 @@ workflow:
 build_http_proxy_image:
   stage: build
   environment:
-    name: $ENV
+    name: build
   tags:
     - build
   variables:
@@ -126,7 +126,7 @@ build_http_proxy_image:
 build_ssh_proxy_image:
   stage: build
   environment:
-    name: $ENV
+    name: build
   tags:
     - build
   variables:
@@ -165,7 +165,7 @@ build_ssh_proxy_image:
 build_login_image:
   stage: build
   environment:
-    name: $ENV
+    name: build
   tags:
     - build
   <<: *build_login_image_template
@@ -176,7 +176,7 @@ build_login_image:
 build_ood_image:
   stage: build
   environment:
-    name: $ENV
+    name: build
   tags:
     - build
   script: