[asan_build] Enable asaned glibc work.

[asan_build] Enable asaned glibc work.

Modify GetPageSize () function to return
4096 for arm and arch64 architectures. We can
not call sysconf from libc befor libc is inited.

Mark libasan as initfirst, in this case "patched" rtld
will be able to initiazlie libasan before libc.so

Change-Id: I56a582fdeafcf55b9dbab8fcd1b39be850cccc04