pw_trace: Add basic sample app

Create a library "sample app", which has 3 fake processes (Kernel,
input, and processing). It then does some tracing in each of these to
give an idea of how different traces could be used.

Kernel: Gives an idea how simple RTOS tracing could be intigrated.
Input: Periodically reads a value, and does some nested operations.
Processing: Has a "job" queue, which forces packets to be processed out
of order and in multiple phases, this gives async-behaviour to the
traces and uses the trace-id to help separate.

Change-Id: I0b25741063785bea60ca5d3225ef199b5656fb2b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/13801
Reviewed-by: (☞゚∀゚)☞ Tennessee Carmel-Veilleux  <tennessee@google.com>
Commit-Queue: Rob Oliver <rgoliver@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 8844c10..c8f937b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -105,6 +105,12 @@
         pw_toolchain_SCOPE.is_host_toolchain && pw_build_HOST_TOOLS) {
       deps += [ ":host_tools" ]
     }
+
+    # Trace examples currently only support running on non-windows host
+    if (defined(pw_toolchain_SCOPE.is_host_toolchain) &&
+        pw_toolchain_SCOPE.is_host_toolchain && host_os != "win") {
+      deps += [ "$dir_pw_trace:trace_example_basic" ]
+    }
   }
 }