IVGCVSW-2000: (Fix) Backend-specific unit tests not being executed

 * Also disabled the Compute_ArmComputeCl/L2Normalization1dNhwc test as it
   fails due to a bug in ACL

Change-Id: If1e36bc04f606e6568e6a13cc77f8f51f5834997
diff --git a/src/backends/cl/test/CMakeLists.txt b/src/backends/cl/test/CMakeLists.txt
index 795a7dc..d365290 100644
--- a/src/backends/cl/test/CMakeLists.txt
+++ b/src/backends/cl/test/CMakeLists.txt
@@ -10,7 +10,7 @@
     ClLayerTests.cpp
 )
 
-add_library(armnnClBackendUnitTests STATIC ${armnnClBackendUnitTests_sources})
+add_library(armnnClBackendUnitTests OBJECT ${armnnClBackendUnitTests_sources})
 target_include_directories(armnnClBackendUnitTests PRIVATE ${PROJECT_SOURCE_DIR}/src)
 target_include_directories(armnnClBackendUnitTests PRIVATE ${PROJECT_SOURCE_DIR}/src/armnn)
 target_include_directories(armnnClBackendUnitTests PRIVATE ${PROJECT_SOURCE_DIR}/src/armnnUtils)
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