vlib: fix os.exec().output usages, that may rely on trimmed lines

cmd/tools/fast/fast.v

@@ -70,7 +70,7 @@ fn main() {
 
 fn exec(s string) string {
 	e := os.exec(s) or { panic(err) }
-	return e.output
+	return e.output.trim_right('\r\n')
 }
 
 // returns milliseconds

cmd/tools/modules/scripting/scripting.v

@@ -58,7 +58,7 @@ pub fn run(cmd string) string {
 	}
 	verbose_trace_exec_result(x)
 	if x.exit_code == 0 {
-		return x.output
+		return x.output.trim_right('\r\n')
 	}
 	return ''
 }