Enable liblog on host bionic

Some of the __BIONIC__ checks were actually looking for an android
device. Host bionic has __BIONIC__, but not __ANDROID__.

Bug: 31559095
Test: Test linux_bionic compile
Change-Id: Ia0ca36fc9486fe8ea7e5d1b2e26ab0491903723c
diff --git a/liblog/Android.bp b/liblog/Android.bp
index 16aa4fa..c498153 100644
--- a/liblog/Android.bp
+++ b/liblog/Android.bp
@@ -73,6 +73,9 @@
         linux: {
             host_ldlibs: ["-lrt"],
         },
+        linux_bionic: {
+            enabled: true,
+        },
     },
 
     cflags: [