Disable IgProf arounds vDSO symbols on AArch64

vDSO on AArch64 is implemented in handwritten assembly and possibly
does not contains unwind information needed for libunwind library to
produce a stack trace. The change disables IgProf profiling in such
code paths.

Signed-off-by: David Abdurachmanov <davidlt@cern.ch>
Merge pull request #48 from davidlt/aarch64-vdso-disable

Disable IgProf arounds vDSO symbols on AArch64.