ci: Switch build-zig to use EC2 (#19487)

Author: Electroid

.buildkite/ci.mjs

@@ -323,9 +323,26 @@ function getCppAgent(platform, options) {
 function getZigAgent(platform, options) {
   const { arch } = platform;
 
-  return {
-    queue: "build-zig",
-  };
+  // Uncomment to restore to using macOS on-prem for Zig.
+  // return {
+  //   queue: "build-zig",
+  // };
+
+  return getEc2Agent(
+    {
+      os: "linux",
+      arch: "x64",
+      abi: "musl",
+      distro: "alpine",
+      release: "3.21",
+    },
+    options,
+    {
+      instanceType: "c7i.2xlarge",
+      cpuCount: 4,
+      threadsPerCore: 1,
+    },
+  );
 }
 
 /**

cmake/tools/SetupZig.cmake

@@ -54,7 +54,14 @@ optionx(ZIG_OBJECT_FORMAT "obj|bc" "Output file format for Zig object files" DEF
 
 optionx(ZIG_LOCAL_CACHE_DIR FILEPATH "The path to local the zig cache directory" DEFAULT ${CACHE_PATH}/zig/local)
 optionx(ZIG_GLOBAL_CACHE_DIR FILEPATH "The path to the global zig cache directory" DEFAULT ${CACHE_PATH}/zig/global)
-optionx(ZIG_COMPILER_SAFE BOOL "Download a ReleaseSafe build of the Zig compiler. Only availble on macos aarch64." DEFAULT ${BUILDKITE})
+
+if(CI AND CMAKE_HOST_APPLE)
+  set(ZIG_COMPILER_SAFE_DEFAULT ON)
+else()
+  set(ZIG_COMPILER_SAFE_DEFAULT OFF)
+endif()
+
+optionx(ZIG_COMPILER_SAFE BOOL "Download a ReleaseSafe build of the Zig compiler. Only availble on macos aarch64." DEFAULT ${ZIG_COMPILER_SAFE_DEFAULT})
 
 setenv(ZIG_LOCAL_CACHE_DIR ${ZIG_LOCAL_CACHE_DIR})
 setenv(ZIG_GLOBAL_CACHE_DIR ${ZIG_GLOBAL_CACHE_DIR})