test: more robust test for dynamically linked lib(std)c++. (#5510)
test: more robust test for dynamically linked lib(std)c++. (#5510)

Notably, this test was previously passing on macOS only because
there is no "libstdc++" or "libgcc" in "ldd: command not found".

Signed-off-by: Piotr Sikora <ba6f3a1a6d7e1ecae91b31e93969cc392fbd0fdd@google.com>
eklitzke/envoy,envoyproxy/envoy,jrajahalme/envoy,dnoe/envoy,lyft/envoy,eklitzke/envoy,lyft/envoy,lizan/envoy,envoyproxy/envoy,jrajahalme/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,dnoe/envoy,envoyproxy/envoy,lyft/envoy,lizan/envoy,lizan/envoy,jrajahalme/envoy,istio/envoy,envoyproxy/envoy-wasm,istio/envoy,envoyproxy/envoy,lizan/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy,eklitzke/envoy,envoyproxy/envoy,jrajahalme/envoy,lyft/envoy,dnoe/envoy,envoyproxy/envoy-wasm,istio/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,jrajahalme/envoy,istio/envoy,istio/envoy,lizan/envoy,istio/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,dnoe/envoy,eklitzke/envoy,dnoe/envoy,envoyproxy/envoy,istio/envoy,lyft/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,lizan/envoy,envoyproxy/envoy-wasm