Make tracing-tracy optional to fix gdb test build failures

The tracing-tracy dependency was causing linker errors in CI due to glibc version incompatibility. Made it optional by:
- Moving tracing-tracy from dev-dependencies to optional dependencies
- Creating a new trace_tracy feature
- Adding required-features to the tracing-tracy example

This prevents tracy from being built during gdb tests, avoiding the linker error with __isoc23_fscanf and __isoc23_strtol symbols.

Co-authored-by: jsturtevant <[email protected]>

Author: Copilot

src/hyperlight_host/Cargo.toml

@@ -40,6 +40,7 @@ tracing = { version = "0.1.43", features = ["log"] }
 tracing-log = "0.2.0"
 tracing-core = "0.1.35"
 tracing-opentelemetry = { version = "0.32.0", optional = true }
+tracing-tracy = { version = "0.11.4", optional = true }
 hyperlight-common = { workspace = true, default-features = true, features = [ "std" ] }
 hyperlight-guest-tracing = { workspace = true, default-features = true, optional = true }
 vmm-sys-util = "0.15.0"
@@ -104,7 +105,6 @@ criterion = "0.8.1"
 tracing-chrome = "0.7.2"
 metrics-util = "0.20.1"
 metrics-exporter-prometheus = { version = "0.18.1", default-features = false }
-tracing-tracy = "0.11.4"
 serde_json = "1.0"
 hyperlight-component-macro = { workspace = true }
 
@@ -130,6 +130,7 @@ print_debug = []
 # Dumps the VM state to a file on unexpected errors or crashes. The path of the file will be printed on stdout and logged.
 crashdump = ["dep:chrono"]
 trace_guest = ["dep:opentelemetry", "dep:tracing-opentelemetry", "dep:hyperlight-guest-tracing", "hyperlight-common/trace_guest"]
+trace_tracy = ["dep:tracing-tracy"]
 mem_profile = [ "trace_guest", "dep:framehop", "dep:fallible-iterator", "hyperlight-common/mem_profile" ]
 kvm = ["dep:kvm-bindings", "dep:kvm-ioctls"]
 mshv3 = ["dep:mshv-bindings", "dep:mshv-ioctls"]
@@ -139,6 +140,10 @@ fuzzing = ["hyperlight-common/fuzzing"]
 build-metadata = ["dep:built"]
 init-paging = []
 
+[[example]]
+name = "tracing-tracy"
+required-features = ["trace_tracy"]
+
 [[bench]]
 name = "benchmarks"
 harness = false