CONFIGURE: Slightly simplify the engines.awk.out generation

There is no need of the she-bang on sourced scripts and eval should be
avoided.
Using a single > allows to not remove the file before writing to it.

configure

@@ -4126,11 +4126,10 @@ append_var MODULES "backends/platform/$_backend"
 # Check if specific components are not used by enabled engines and disable them
 #
 echo "Checking for unused components..."
-rm -f engines.awk.out
 awk -f "$_srcdir/engines.awk" -v _pass=pass1 < /dev/null
 echo "...check complete"
 
-eval "`. engines.awk.out`"
+. ./engines.awk.out
 
 for f in $_features_disabled; do
     set_var $(get_var _feature_${f}_settings) "no"

engines.awk

@@ -380,7 +380,7 @@ END {
 			}
 		}
 
-		print("#!/bin/sh\necho '_features_disabled=\"" _features_disabled "\"'") >> "engines.awk.out"
+		print("_features_disabled=\"" _features_disabled "\"") > "engines.awk.out"
 
 		exit 0
 	}