Attempt CI fix #2

.drone.yml

@@ -2,14 +2,11 @@ kind: pipeline
 type: docker
 name: continuous integration
 
-environment:
-  ZIG_VERSION: 0.13.0
-
 steps:
   - name: setup
     image: ubuntu:latest
     environment:
-      ZIG_VERSION: ${ZIG_VERSION}
+      ZIG_VERSION: 0.13.0
     commands:
       - apt-get update
       - apt-get install -y xz-utils wget libsdl2-dev glslang-tools spirv-tools
@@ -21,7 +18,7 @@ steps:
   - name: build
     image: ubuntu:latest
     environment:
-      ZIG_VERSION: ${ZIG_VERSION}
+      ZIG_VERSION: 0.13.0
     commands:
       - export PATH=$PATH:$(pwd)/zig-linux-x86_64-${ZIG_VERSION}
       - zig build
@@ -29,7 +26,7 @@ steps:
   - name: test
     image: ubuntu:latest
     environment:
-      ZIG_VERSION: ${ZIG_VERSION}
+      ZIG_VERSION: 0.13.0
     commands:
       - export PATH=$PATH:$(pwd)/zig-linux-x86_64-${ZIG_VERSION}
       - zig build test