Do not reference PTRACE_{G,S}ETFPXREGS when undefined

Created by: umarcor

Issue: #3381 (closed) Issue: #3399 (closed)

Signed-off-by: Unai Martinez-Corral unai.martinezcorral@ehu.eus

---

Building on armv7l or armv8l fails with:

[ 64%] Building C object core/CMakeFiles/drinjectlib.dir/config.c.o
/dynamorio/core/unix/injector.c:866:50: error: 'PTRACE_GETFPXREGS' undeclared here (not in a function)
                                                { PTRACE_GETFPXREGS, "PTRACE_GETFPXREGS" },
                                                  ^~~~~~~~~~~~~~~~~
/dynamorio/core/unix/injector.c:867:50: error: 'PTRACE_SETFPXREGS' undeclared here (not in a function)
                                                { PTRACE_SETFPXREGS, "PTRACE_SETFPXREGS" },
                                                  ^~~~~~~~~~~~~~~~~
make[2]: *** [core/CMakeFiles/drinjectlib.dir/unix/injector.c.o] Error 1

This PR avoids using PTRACE_GETFPXREGS and PTRACE_SETFPXREGS on ARM, as it is currently done on AARCH64.