Remove Buildarch from ldflags, use runtime.GOARCH instead

The architecture is available at runtime via stdlib, no need to bake
it in at build time.

internal/logger/logger.go

@@ -4,6 +4,7 @@ package logger
 import (
 	"log/slog"
 	"os"
+	"runtime"
 
 	"go.uber.org/fx"
 	"sneak.berlin/go/pixa/internal/globals"
@@ -72,6 +73,6 @@ func (l *Logger) Identify() {
 	l.log.Info("starting",
 		"appname", l.globals.Appname,
 		"version", l.globals.Version,
-		"buildarch", l.globals.Buildarch,
+		"arch", runtime.GOARCH,
 	)
 }