Force GOTOOLCHAIN=auto so CI can build the go1.25 module graph

The prow build root ships go 1.23 with GOTOOLCHAIN=local, while the
compliance-operator v1.9.0 / k8s v0.35 dependency stack requires go >=
1.25.3, so every lane fails at compile. Override GOTOOLCHAIN in the
Makefile so go downloads the matching toolchain; can be dropped once the
openshift/release build root moves to a golang-1.25 image.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Vincent056

Makefile

@@ -25,6 +25,11 @@ CONTENT_IMAGE_FLAG:=$(if $(strip $(CONTENT_IMAGE)),-content-image="$(CONTENT_IMA
 LOG_DIR?=
 LOG_DIR_FLAG:=$(if $(strip $(LOG_DIR)),-log-dir="$(LOG_DIR)")
 
+# The CI build root pins GOTOOLCHAIN=local with a Go older than go.mod requires
+# (compliance-operator v1.9.0 and the k8s v0.35 stack need go >= 1.25.3). Let go
+# download the matching toolchain instead of failing the build.
+export GOTOOLCHAIN := auto
+
 GOLANGCI_LINT_VERSION=latest
 BUILD_DIR := build
 PLATFORM?=ocp