Update default C++ standard to C++14

(3RDPARTY_UPDATE)

Resolves: COMPMID-3849

Signed-off-by: Georgios Pinitas <georgios.pinitas@arm.com>
Change-Id: I6369f112337310140e2d6c8e79630cd11138dfa0
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/4544
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michalis Spyrou <michalis.spyrou@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/SConstruct b/SConstruct
index 4be00f3..395fb5e 100644
--- a/SConstruct
+++ b/SConstruct
@@ -146,7 +146,7 @@
 env.Append(CXXFLAGS = ['-Wall','-DARCH_ARM',
          '-Wextra','-pedantic','-Wdisabled-optimization','-Wformat=2',
          '-Winit-self','-Wstrict-overflow=2','-Wswitch-default',
-         '-std=gnu++11','-Woverloaded-virtual', '-Wformat-security',
+         '-std=c++14','-Woverloaded-virtual', '-Wformat-security',
          '-Wctor-dtor-privacy','-Wsign-promo','-Weffc++','-Wno-overlength-strings'])
 
 env.Append(CPPDEFINES = ['_GLIBCXX_USE_NANOSLEEP'])