pw_interrupt: Extend CMake support

Change-Id: I3604043f61a7db887cd8065c825da99ee7bcf6c0
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/79468
Pigweed-Auto-Submit: Ewout van Bekkum <ewout@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_interrupt/CMakeLists.txt b/pw_interrupt/CMakeLists.txt
index 87536f0..f162729 100644
--- a/pw_interrupt/CMakeLists.txt
+++ b/pw_interrupt/CMakeLists.txt
@@ -14,4 +14,9 @@
 
 include($ENV{PW_ROOT}/pw_build/pigweed.cmake)
 
-pw_add_facade(pw_interrupt)
+pw_add_facade(pw_interrupt.context
+  HEADERS
+    public/pw_interrupt/context.h
+  PUBLIC_INCLUDES
+    public
+)