More CI (#3)

- ci only: use a separate zig cache dir for each run
- use `tools/bazel` everywhere.
- remove arm64 tests. They don't give enough value to be worth the
  brittle environment.
- remove windows execution, except for launcher. Ditto. I will probably
  bring them back.

test/windows/BUILD

@@ -9,12 +9,19 @@ cc_binary(
     tags = ["manual"],
 )
 
-platform_test(
+# TODO(motiejus): bring back windows tests, not only builds
+#platform_test(
+#    name = "winver_windows_amd64",
+#    src = "winver",
+#    platform = "//platform:windows_amd64",
+#    run_under = "wine64-stable",
+#    tags = ["no-sandbox"],
+#)
+
+platform_binary(
     name = "winver_windows_amd64",
     src = "winver",
     platform = "//platform:windows_amd64",
-    run_under = "wine64-stable",
-    tags = ["no-sandbox"],
 )
 
 platform_binary(