Add test for first diagnostic (different OS/arch)

go/ql/integration-tests/all-platforms/go/diagnostics/build-constraints-exclude-all-go-files/diagnostics.expected

@@ -0,0 +1,15 @@
+{
+  "internal": false,
+  "markdownMessage": "Make sure the `GOOS` and `GOARCH` [environment variables are correctly set](https://docs.github.com/en/actions/learn-github-actions/variables#defining-environment-variables-for-a-single-workflow). Alternatively, [change your OS and architecture](https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#using-a-github-hosted-runner)",
+  "severity": "warning",
+  "source": {
+    "extractorName": "go",
+    "id": "go/extractor/package-different-os-architecture",
+    "name": "Package syscall/js is intended for a different OS or architecture"
+  },
+  "visibility": {
+    "cliSummaryTable": true,
+    "statusPage": true,
+    "telemetry": true
+  }
+}

go/ql/integration-tests/all-platforms/go/diagnostics/build-constraints-exclude-all-go-files/test.py

@@ -0,0 +1,9 @@
+import sys
+
+from create_database_utils import *
+from diagnostics_test_utils import *
+
+os.environ['LGTM_INDEX_IMPORT_PATH'] = "test"
+run_codeql_database_create([], lang="go", source="work", db=None)
+
+check_diagnostics()

go/ql/integration-tests/all-platforms/go/diagnostics/build-constraints-exclude-all-go-files/work/go.mod

@@ -0,0 +1,3 @@
+go 1.18
+
+module test

go/ql/integration-tests/all-platforms/go/diagnostics/build-constraints-exclude-all-go-files/work/test.go

@@ -0,0 +1,8 @@
+package test
+
+import "syscall/js"
+
+func Test() {
+	var x js.Error
+	_ = x
+}