nfs-utils: needs mmu

Fix below build error:

mountd-mountd.o: In function `main':
mountd.c:(.text+0x1264): undefined reference to `fork'
mountd.c:(.text+0x1320): undefined reference to `fork'
mountd-rmtab.o: In function `ha_callout':
rmtab.c:(.text+0xa8): undefined reference to `fork'
collect2: ld returned 1 exit status
make[3]: *** [mountd] Error 1

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/nfs-utils/Config.in

@@ -3,6 +3,7 @@ config BR2_PACKAGE_NFS_UTILS
 	depends on BR2_TOOLCHAIN_HAS_NATIVE_RPC || BR2_TOOLCHAIN_HAS_THREADS # libtirpc
 	select BR2_PACKAGE_LIBTIRPC if !BR2_TOOLCHAIN_HAS_NATIVE_RPC
 	depends on BR2_LARGEFILE
+	depends on BR2_USE_MMU # fork()
 	help
 	  The NFS Linux kernel server.
 	  Warning: We do not force largefile support on here on purpose.