fmsg: implement suspend in writer

This removes the requirement to call fmsg.Exit on every exit path, and enables direct use of the "log" package. However, fmsg.BeforeExit is still encouraged when possible to catch exit on suspended output.

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

internal/app/seal.go

@@ -191,7 +191,7 @@ func (a *app) Seal(config *fst.Config) error {
 
 	// map sandbox config to bwrap
 	if config.Confinement.Sandbox == nil {
-		fmsg.VPrintln("sandbox configuration not supplied, PROCEED WITH CAUTION")
+		fmsg.Verbose("sandbox configuration not supplied, PROCEED WITH CAUTION")
 
 		// permissive defaults
 		conf := &fst.SandboxConfig{
@@ -264,7 +264,7 @@ func (a *app) Seal(config *fst.Config) error {
 	}
 
 	// verbose log seal information
-	fmsg.VPrintf("created application seal for uid %s (%s) groups: %v, command: %s",
+	fmsg.Verbosef("created application seal for uid %s (%s) groups: %v, command: %s",
 		seal.sys.user.us, seal.sys.user.username, config.Confinement.Groups, config.Command)
 
 	// seal app and release lock