agent: add separate glibc build with NVML support (#1618)

purego requires dynamic linking, so split the agent builds:
- Default: static binary without NVML (works on musl/alpine)
- Glibc: dynamic binary with NVML support via purego

Changes:
- Add glibc build tag to conditionally include NVML code
- Add beszel-agent-linux-amd64-glibc build/archive in goreleaser
- Update ghupdate to use glibc binary on glibc systems
- Switch nvidia dockerfile to golang:bookworm with -tags glibc

agent/gpu.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"log/slog"
 	"maps"
 	"os/exec"
 	"regexp"
@@ -14,8 +15,6 @@ import (
 	"time"
 
 	"github.com/henrygd/beszel/internal/entities/system"
-
-	"log/slog"
 )
 
 const (