Build recovery variant of the dynamic linker

In order to support shared libraries in the recovery mode, the dynamic
linker is now built with recovery_available: true option.

In addition, a few more modules (such as libasync, etc.) are also marked
as recovery_available: true as they are transitive dependencies of the
dynamic linker.

Bug: 63673171
Test: `adb reboot recovery; adb devices` shows the device ID
Test: `adb root && adb shell` and then
$ lsof -p `pidof adbd` shows that libm.so, libc.so, etc. are loaded from
the /lib directory.

Change-Id: Idd981d8cf25568a85b24032cf78e50adfd5f4a7f
diff --git a/libc/async_safe/Android.bp b/libc/async_safe/Android.bp
index a835697..29f90d1 100644
--- a/libc/async_safe/Android.bp
+++ b/libc/async_safe/Android.bp
@@ -9,6 +9,7 @@
 
     name: "libasync_safe",
     vendor_available: true,
+    recovery_available: true,
 
     include_dirs: ["bionic/libc"],