Fix bionic benchmarks and header tests for musl

Fix references to symbols that don't exist in musl in the bionic
benchmarks, and disable the header tests for musl.

Bug: 190084016
Test: m USE_HOST_MUSL=true host-native
Change-Id: I6b1964afa4a7b6e6a4812e9f2605fcfc2fae9691
diff --git a/tests/headers/posix/Android.bp b/tests/headers/posix/Android.bp
index 0809cdb..4a20d45 100644
--- a/tests/headers/posix/Android.bp
+++ b/tests/headers/posix/Android.bp
@@ -33,5 +33,8 @@
         darwin: {
             enabled: false,
         },
+        musl: {
+            enabled: false,
+        },
     },
 }