fio: depends on BR2_TOOLCHAIN_HAS_SYNC_4

It uses __sync_fetch_and_add_4() and other 32-bit atomics, fixes:
http://autobuild.buildroot.net/results/692/692fe7999efb63a2bffee02f84b9f636afcfe5f4/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/fio/Config.in

@@ -2,6 +2,7 @@ config BR2_PACKAGE_FIO
 	bool "fio"
 	depends on BR2_USE_MMU # fork()
 	depends on !BR2_STATIC_LIBS
+	depends on BR2_TOOLCHAIN_HAS_SYNC_4
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	# fio uses posix_madvise(), which is not part of any official
 	# release of uClibc, but is part of uClibc Git, and backported
@@ -20,5 +21,6 @@ config BR2_PACKAGE_FIO
 
 comment "fio needs a toolchain w/ dynamic library, threads"
 	depends on !BR2_TOOLCHAIN_HAS_THREADS || BR2_STATIC_LIBS
+	depends on BR2_TOOLCHAIN_HAS_SYNC_4
 	depends on !BR2_nios2
 	depends on BR2_USE_MMU