Rename libunwind -> libunwind_shared

The LLVM build system produces a libunwind.a, and the Clang driver
links its libunwind.a automatically when -nostdlib isn't passed. I'd
like to keep the libunwind.a name, but adding a Soong prebuilt module
of name "libunwind" conflicts with the external/libunwind module that
practically no one is using.

Fix the conflict by renaming libunwind to libunwind_shared, and
removing unnecessary uses of the old module.

(Code should use to collect backtraces, and it should
use's _Unwind_* APIs for C++ exception handling unwinding.)

Test: build Android
Change-Id: Idc4e5fca7f0a4b2dc59493b3956787b841662f9f
Merged-In: Idc4e5fca7f0a4b2dc59493b3956787b841662f9f
(cherry picked from commit 7bfc066a96945e78fee43b104815dcf5165b067c)
diff --git a/Android.bp b/Android.bp
index b63a44b..6f0a4eb 100644
--- a/Android.bp
+++ b/Android.bp
@@ -335,7 +335,7 @@
 cc_library_shared {
-    name: "libunwind",
+    name: "libunwind_shared",
     defaults: ["libunwind_core_defaults"],
@@ -403,7 +403,7 @@
     local_include_dirs: ["include"],
-    shared_libs: ["libunwind"],
+    shared_libs: ["libunwind_shared"],