Add missing host ldlibs

Host builds were compiling without -Wl,--no-undefined.  Add missing
host ldlibs so that -Wl,--no-undefined can be added again.

Test: m -j host
Bug: 32305815
Change-Id: I0ceabc3f4ec74e2f737afaac58810c5d53d6ccb6
diff --git a/libbacktrace/Android.bp b/libbacktrace/Android.bp
index 85b5597..5c72234 100644
--- a/libbacktrace/Android.bp
+++ b/libbacktrace/Android.bp
@@ -92,6 +92,7 @@
             ],
 
             static_libs: ["libcutils"],
+            host_ldlibs: ["-lrt"],
         },
         android: {
             srcs: libbacktrace_sources,