Add ARM EABI function __aeabi_read_tp

By default, Clang uses this arm32 function to read the thread pointer,
either for ELF TLS or via __builtin_thread_pointer(). It's probably better
to inline the cp15 access using -mtp=cp15, but that's not the default yet.

See https://reviews.llvm.org/D34878?id=114573.

Bug: http://b/78026329
Test: bionic unit tests
Change-Id: I93b8926075f0b2cea8df9ef518d54f2820a8ff5b
diff --git a/tests/Android.bp b/tests/Android.bp
index 899fc66..7d56a22 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -64,6 +64,7 @@
     name: "libBionicStandardTests",
     defaults: ["bionic_tests_defaults"],
     srcs: [
+        "__aeabi_read_tp_test.cpp",
         "alloca_test.cpp",
         "android_get_device_api_level.cpp",
         "arpa_inet_test.cpp",