package/optee-benchmark: needs fork

Fixes:
 - http://autobuild.buildroot.org/results/ea61442275d1790a29e02e2fa27f072e4c12daa7

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/optee-benchmark/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_OPTEE_BENCHMARK
 	bool "optee-benchmark"
+	depends on BR2_USE_MMU # fork()
 	depends on BR2_TOOLCHAIN_HAS_THREADS # optee-client
 	select BR2_PACKAGE_OPTEE_CLIENT
 	select BR2_PACKAGE_LIBYAML
@@ -12,4 +13,5 @@ config BR2_PACKAGE_OPTEE_BENCHMARK
 	  http://github.com/linaro-swg/optee_benchmark
 
 comment "optee-benchmark needs a toolchain w/ threads"
+	depends on BR2_USE_MMU
 	depends on !BR2_TOOLCHAIN_HAS_THREADS