Break libdl.so and ld-android.so's dependency on libc.so.

 * Specify "nocrt: true" to avoid calling __cxa_finalize.

 * Define a dummy __aeabi_unwind_cpp_pr0 for arm32.

Bug: b/62815515
Bug: b/73873002
Test: boot AOSP hikey960-userdebug
Test: run ndk_cxa_example in special /system/bin/debug namespace
Test: run Bionic unit tests
Change-Id: I59bcb100a2753286b59c51a47d7a183507219a07
(cherry picked from commit 470b6664)