COMPMID-1246: Add -Wno-implicit-fallthrough flag on gcc compilation

Change-Id: I419ea7c97aa3a85bd13e5c124c4d89eb07321e73
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/138456
Reviewed-by: Vidhya Sudhan Loganathan <vidhyasudhan.loganathan@arm.com>
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: Jenkins <bsgcomp@arm.com>
diff --git a/SConstruct b/SConstruct
index f72c568..ccc9216 100644
--- a/SConstruct
+++ b/SConstruct
@@ -106,7 +106,7 @@
 if 'clang++' in cpp_compiler:
     env.Append(CXXFLAGS = ['-Wno-format-nonliteral','-Wno-deprecated-increment-bool','-Wno-vla-extension','-Wno-mismatched-tags'])
 else:
-    env.Append(CXXFLAGS = ['-Wlogical-op','-Wnoexcept','-Wstrict-null-sentinel'])
+    env.Append(CXXFLAGS = ['-Wlogical-op','-Wnoexcept','-Wstrict-null-sentinel','-Wno-implicit-fallthrough'])
 
 if env['cppthreads']:
     env.Append(CPPDEFINES = [('ARM_COMPUTE_CPP_SCHEDULER', 1)])