Move sigrtmin.h into platform headers.

Test: mma
Change-Id: Ibc97ef96fe9e32b948c245b06039b95fe4342f39
diff --git a/libc/Android.bp b/libc/Android.bp
index d418012..6d4b719 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1808,6 +1808,7 @@
         "//frameworks:__subpackages__",
         "//external/perfetto:__subpackages__",
         "//external/scudo:__subpackages__",
+        "//system/core/debuggerd:__subpackages__",
     ],
     host_supported: true,
     recovery_available: true,