Fix nightly test failure

* Both macros ARM_COMPUTE_ENABLE_FP16 and ENABLE_FP16_KERNELS
  must be declared to enable FP16

* The failure was caused by not compiling the validation suite with the same
  definitions used to compile the library. ARM_COMPUTE_ENABLE_FP16 was missing
  and the call from the test into error_on_unsupported_cpu_fp16() failed.

* Resolves COMPMID-6727

Change-Id: I278c813aef799d9d0e21e5323b2b8e9e45252d6c
Signed-off-by: Pablo Marquez Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/10848
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: SiCong Li <sicong.li@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>
diff --git a/SConscript b/SConscript
index 31e7a5b..6ad4c78 100644
--- a/SConscript
+++ b/SConscript
@@ -86,9 +86,10 @@
     lib_static_objs = [] # static objects
     lib_shared_objs = [] # shared objects
 
+    # note that ARM_COMPUTE_ENABLE_FP16 is enabled in update_data_type_layout_flags() to make
+    # sure the environment is progated to the validation suite
     arm_compute_env.Append(CPPDEFINES = ['ENABLE_NEON', 'ARM_COMPUTE_ENABLE_NEON',
-                           'ENABLE_SVE', 'ARM_COMPUTE_ENABLE_SVE',
-                           'ARM_COMPUTE_ENABLE_FP16', 'ARM_COMPUTE_ENABLE_BF16',
+                           'ENABLE_SVE', 'ARM_COMPUTE_ENABLE_SVE','ARM_COMPUTE_ENABLE_BF16',
                            'ARM_COMPUTE_ENABLE_I8MM', 'ARM_COMPUTE_ENABLE_SVEF32MM'])
 
     # Build all the common files for the base architecture