tests: lib: spsc_pbuf: Do not run test with cache

Test was using a configuration which enforces cache management in the
packet buffer. However it shall not be used if producer and consumer
is the same core. Testing this configuration on a single core does
not make sense as it actually fails on cores with data cache.

Making this configuration build_only so it is checked against
compilation errors.

Signed-off-by: Krzysztof Chruściński <[email protected]>

Author: nordic-krch

tests/lib/spsc_pbuf/testcase.yaml

@@ -9,9 +9,10 @@ tests:
   libraries.spsc_pbuf.cache:
     integration_platforms:
       - native_sim
-    # Exclude platform which does not link with cache functions
-    platform_exclude: ast1030_evb
-    timeout: 120
+    # This configuration only make sense for interprocessor data sharing so
+    # configuration can only be verified against compilation errors on a single core.
+    platform_allow: native_sim
+    build_only: true
     extra_configs:
       - CONFIG_SPSC_PBUF_CACHE_ALWAYS=y