Compilation under fedora 28

[lucag73]

PCSX2 version:
Git release: 4de2df2
Description of the issue:
Compilation of pcsx2 with gcc8 in Fedora28 fails since _xgetbv is already defined

How to reproduce the issue:

1. install fedora 28 (with all of the relevant packages for compiling pcsx2)
2. build with ./build.sh --release --gtk3
3. the compilation fails as soon as common/include/x86emitter/x86_intrin.h is included

The issue can be fixed by adding in the aforementioned file a
#define _XSAVEINTRIN_H_INCLUDED
which prevents the inclusion of /usr/lib/gcc/x86_64-redhat-linux/8/include/xsaveintrin.h
but this is clearly a hack.

[gregory38]

We need to check how _xgetbv is implemented on gcc8 and remove our definition if already defined or if gcc >= 8

[gregory38]

Yes we should use gcc implementation by default

[turtleli]

#2419 should fix the issue.

[lucag73]

I posted in #2419 ... with this fix compilation works, but pcsx2 segfaults on start...