Fixes android build error:

bdev/bdev.c: In function 'detect_fs':
bdev/bdev.c:686:2: error: implicit declaration of function 'getline' [-Werror=implicit-function-declaration]
  while (getline(&line, &linelen, f) != -1) {
  ^
Signed-off-by: Christian Brauner <cbrauner@suse.de>