core/xfa: disable asan on llvm

[Teufelchen1]

Contribution description

Hi! 🦎

When using llvm and address sanitation, the XFA trip the sanitizer.
This PR attempts to fix this by adding the no_sanitize attribute to the XFA macros. Sadly, this attribute is not known by gnu, a guard is hence needed. I'm open for alternatives as I dislike this solution but it is the best I could come up with.

Testing procedure

Before this patch:

Go to examples/gnrc_minimal and run TOOLCHAIN=llvm make all-asan and then make term.
You should see an error similar to this:

==3374719==ERROR: AddressSanitizer: global-buffer-overflow on address 0x080774e0 at pc 0x0804af5e bp 0x0808eb88 sp 0x0808eb78
READ of size 4 at 0x080774e0 thread T0
    #0 0x804af5d in _auto_init_module /RIOT/sys/auto_init/auto_init.c:40
    #1 0x804af5d in auto_init /RIOT/sys/auto_init/auto_init.c:339
    #2 0x804b375 in main_trampoline /RIOT/core/lib/init.c:56
    #3 0xf76bc7b8 in makecontext (/lib32/libc.so.6+0x4a7b8)
...

After applying this PR, the example can be build and run with llvm or gcc, with or without asan.

[riot-ci]

Murdock results

✔️ PASSED

a8c9af9 core/xfa: disable asan on llvm

Success	Failures	Total	Runtime
6865	0	6865	15m:25s

Artifacts

• Documentation preview

[benpicco]

Looks good to me!

[bors]

🕐 Waiting for PR status (GitHub check) to be set, probably by CI. Bors will automatically try to run when all required PR statuses are set.

[benpicco]

bors merge

[bors]

Stopped waiting for PR status (GitHub check) without running due to duplicate requests to run. You may check Bors to see that this PR is included in a batch by one of the other requests.

[bors]

Build succeeded:

• Murdock
• static-tests
• tools-build-success