helper/bwrap: allocate large args slice

Signed-off-by: Ophestra <cat@gensokyo.uk>

helper/bwrap/arg.go

@@ -54,6 +54,11 @@ func (c *Config) Args() (args []string) {
 		c.pairArgs(),
 	}
 
+	/* this is only 8 KiB of memory on a 64-bit system,
+	permissive defaults on NixOS results in around 200 args
+	so this capacity should eliminate copies for most setups */
+	args = make([]string, 0, 512)
+
 	// copy FSBuilder slice to builder slice
 	fb := make([]Builder, len(c.Filesystem)+1)
 	for i, f := range c.Filesystem {