Switch libc to libcrt.builtins

With the switch to libcrt.builtins, some symbols no longer becomes
exported. Add dummy references to them to force them to be exported.
This is to maintain backwards binary compatibility with ancient Android
versions.

x86 and x86_64 crashes with libcrt, keep using libgcc for now.

Test: bionic-unit-tests
Bug: 29275768
Bug: 122993569
Change-Id: Ieab5af354e3924af4a03d888b28c6e75090cb613
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 6a6ea7d..62aea27 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1561,7 +1561,7 @@
     __ashldi3; # arm
     __ashrdi3; # arm
     __bionic_brk; # arm x86 mips
-    __bionic_libgcc_compat_symbols; # arm x86
+    __bionic_libcrt_compat_symbols; # arm x86
     __cmpdf2; # arm
     __divdf3; # arm
     __divdi3; # arm x86 mips