Revert "libbb: remove unnecessary variable in xmalloc_fgets"

The variable is in fact necessary.

    commit 2da9724b
    Author: Quentin Rameau <quinq@fifth.space>
    Date:   Sun Apr 1 17:05:35 2018 +0200
        libbb: remove unnecessary variable in xmalloc_fgets
Signed-off-by: NDenys Vlasenko <vda.linux@googlemail.com>

libbb/get_line_from_file.c

@@ -47,7 +47,9 @@ char* FAST_FUNC bb_get_chunk_from_file(FILE *file, size_t *end)
 /* Get line, including trailing \n if any */
 char* FAST_FUNC xmalloc_fgets(FILE *file)
 {
-	return bb_get_chunk_from_file(file, NULL);
+	size_t i;
+
+	return bb_get_chunk_from_file(file, &i);
 }
 /* Get line.  Remove trailing \n */
 char* FAST_FUNC xmalloc_fgetline(FILE *file)