Initialize __libc_sysinfo early on.

__libc_sysinfo is hidden, so accessing it doesn't require a relocated GOT.
It is important not to have a relocatable initializer on __libc_sysinfo,
because if it did have one, and if we initialized it before relocating the
linker, then on 32-bit x86 (which uses REL rather than RELA), the
relocation step would calculate the wrong addend and overwrite
__libc_sysinfo with garbage.

Asides:

 * It'd be simpler to keep the __libc_sysinfo initializer for static
   executables, but the loader pulls in libc_init_static (even though it
   uses almost none of the code in that file, like __libc_init).

 * The loader has called __libc_init_sysinfo three times by the time it
   has relocated itself. A static executable calls it twice, while libc.so
   calls it only once.

Bug: none
Test: lunch aosp_x86-userdebug ; emulator
Test: adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
Test: adb shell /data/nativetest/bionic-unit-tests-static/bionic-unit-tests-static
Change-Id: I5944f57847db7191608f4f83dde22b49e279e6cb