local backend ignore errors in commands inbetween (#2636)

for normal posix shells we have to add the `-e ` option ... but as there
are more shells out there we have to handle this edgecases on base per
base case.

create a switch case statement in woodpecker should be fine as there is
only a finite number of shells, used in production.

also close  #2612

---
*Sponsored by Kithara Software GmbH*

pipeline/backend/common/script.go

@@ -37,10 +37,3 @@ func GenerateContainerConf(commands []string) (env map[string]string, entry, cmd
 
 	return env, entry, cmd
 }
-
-func GenerateScript(commands []string) string {
-	if runtime.GOOS == "windows" {
-		return generateScriptWindows(commands)
-	}
-	return generateScriptPosix(commands)
-}