Move platform-private symbols out of libdl.so

Symbols not intended to be accessible from apps are moved to libdl_android.so

Test: bionic-unit-tests
Bug: http://b/129387775
Change-Id: Ib8ba6147a20cf56550c9a008f66570a2d419565a
(cherry picked from commit 2d6be9a751685b4c307632bf27e8c100310ad500)
diff --git a/libdl/Android.bp b/libdl/Android.bp
index 2e171d6..a41aa2d 100644
--- a/libdl/Android.bp
+++ b/libdl/Android.bp
@@ -110,6 +110,72 @@
     },
 }
 
+cc_library {
+    name: "libdl_android",
+
+    defaults: ["linux_bionic_supported"],
+
+    // NOTE: --exclude-libs=libgcc.a makes sure that any symbols libdl.so pulls from
+    // libgcc.a are made static to libdl.so.  This in turn ensures that libraries that
+    // a) pull symbols from libgcc.a and b) depend on libdl.so will not rely on libdl.so
+    // to provide those symbols, but will instead pull them from libgcc.a.  Specifically,
+    // we use this property to make sure libc.so has its own copy of the code from
+    // libgcc.a it uses.
+    //
+    // DO NOT REMOVE --exclude-libs!
+
+    ldflags: [
+        "-Wl,--exclude-libs=libgcc.a",
+        "-Wl,--exclude-libs=libclang_rt.builtins-arm-android.a",
+        "-Wl,--exclude-libs=libclang_rt.builtins-aarch64-android.a",
+        "-Wl,--exclude-libs=libclang_rt.builtins-x86-android.a",
+        "-Wl,--exclude-libs=libclang_rt.builtins-x86_64-android.a",
+    ],
+
+    // for x86, exclude libgcc_eh.a for the same reasons as above
+    arch: {
+        x86: {
+            ldflags: [
+                "-Wl,--exclude-libs=libgcc_eh.a",
+            ],
+        },
+        x86_64: {
+            ldflags: ["-Wl,--exclude-libs=libgcc_eh.a"],
+        },
+    },
+
+    srcs: [ "libdl_android.cpp" ],
+    version_script: "libdl_android.map.txt",
+
+    cflags: [
+        "-Wall",
+        "-Wextra",
+        "-Wunused",
+        "-Werror",
+    ],
+
+    stl: "none",
+
+    nocrt: true,
+    system_shared_libs: [],
+
+    // Opt out of native_coverage when opting out of system_shared_libs
+    native_coverage: false,
+
+    // This is placeholder library the actual implementation is (currently)
+    // provided by the linker.
+    shared_libs: ["ld-android"],
+
+    sanitize: {
+        never: true,
+    },
+
+    stubs: {
+        symbol_file: "libdl_android.map.txt",
+        versions: ["10000"],
+    },
+}
+
 ndk_library {
     name: "libdl",
     symbol_file: "libdl.map.txt",