Depend on libasync_safe module instead of breaking package boundary.

This makes Bazel conversion easier (because in Bazel package boundaries really matter).

Test: m libc still builds, and m also builds.
Change-Id: I5cfc9d83dffd3110ffad9ce03198e6141c8c5b33

libc/Android.bp

diff --git a/libc/Android.bp b/libc/Android.bp
index df8871a..e1916b9 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -21,7 +21,6 @@
 }
 
 libc_common_src_files = [
-    "async_safe/async_safe_log.cpp",
     "bionic/ether_aton.c",
     "bionic/ether_ntoa.c",
     "bionic/exit.cpp",
@@ -1420,6 +1419,7 @@
     whole_static_libs: [
         "gwp_asan",
         "libarm-optimized-routines-string",
+        "libasync_safe",
         "libc_bionic_ndk",
         "libc_bootstrap",
         "libc_fortify",
@@ -1451,6 +1451,7 @@
 
     whole_static_libs: [
         "libarm-optimized-routines-string",
+        "libasync_safe",
         "libc_bionic",
         "libc_bionic_ndk",
         "libc_bootstrap",