eval: don't build trace message when tracing disabled #11131

Job	Run time
YAML Lint	20s
Go Lint	1m 33s
Generate Code	1m 18s
Rego PR checks	1m 27s
Check Generated	26s
Go Test (linux)	4m 32s
WASM	11s
Go Build (linux amd64)	2m 25s
Go Test (darwin)	4m 15s
Go compat build/test (ubuntu-22.04, 1.21)	3m 46s
Go Build (linux arm64)	2m 9s
Go Race Detector	6m 30s
Go Build (linux arm64GO_TAGS="-tags=opa_no_oci")	2m 13s
Go compat build/test (macos-14, 1.21)	4m 18s
Go Build (windows amd64)	2m 27s
Go Build (darwin amd64)	2m 2s
Go Build (darwin arm64)	41s
docker image smoke test	25s
smoke-test-binaries (linux, ubuntu-22.04, opa_linux_amd64, amd64)	11s
smoke-test-binaries (linux, ubuntu-22.04, opa_linux_amd64_static, amd64, disabled)	9s
smoke-test-binaries (darwin, macos-13, opa_darwin_amd64, amd64)	40s
smoke-test-binaries (darwin, macos-14, opa_darwin_arm64_static, arm64, disabled)	14s
smoke-test-binaries (windows, windows-latest, opa_windows_amd64.exe, amd64)	33s
	42m 45s

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