Do not ignore error when writing environment file

Test: m nothing
Change-Id: I4281e22ae10a649b51b9fbed7f8c1554f18885b9
diff --git a/ui/build/soong.go b/ui/build/soong.go
index fc43663..242282b 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -110,7 +110,10 @@
 		soongBuildEnv.Set("SOONG_DELVE_PATH", shared.ResolveDelveBinary())
 	}
 
-	writeEnvironmentFile(ctx, envFile, soongBuildEnv.AsMap())
+	err := writeEnvironmentFile(ctx, envFile, soongBuildEnv.AsMap())
+	if err != nil {
+		ctx.Fatalf("failed to write environment file %s: %s", envFile, err)
+	}
 
 	func() {
 		ctx.BeginTrace(metrics.RunSoong, "environment check")