src: ittnotify: ittnotify_static: resolve Wundef hits

[dzarukin]

Some projects that include oneDNN use -Wundef compilation flag. oneDNN decided to add the flag into the build as well and it automatically promoted to third_party dependencies including ittnotify.

Macros that may not be defined must be checked for presence first.

[eparshut]

@dzarukin, Thanks for your contribution!

After adding the -Wundef flag I see 3 hits:

Building C object CMakeFiles/ittnotify.dir/src/ittnotify/ittnotify_static.c.o
/localdisk3/eparshut/temp/wundef_ittapi/src/ittnotify/ittnotify_static.c:59:64: warning: "__cplusplus" is not defined, evaluates to 0 [-Wundef]
   59 | #if (HAS_CPP_ATTR(fallthrough) || HAS_C_ATTR(fallthrough)) && (__cplusplus >= 201703L || _MSVC_LANG >= 201703L)
      |                                                                ^~~~~~~~~~~
/localdisk3/eparshut/temp/wundef_ittapi/src/ittnotify/ittnotify_static.c:59:90: warning: "_MSVC_LANG" is not defined, evaluates to 0 [-Wundef]
   59 | #if (HAS_CPP_ATTR(fallthrough) || HAS_C_ATTR(fallthrough)) && (__cplusplus >= 201703L || _MSVC_LANG >= 201703L)
      |                                                                                          ^~~~~~~~~~
/localdisk3/eparshut/temp/wundef_ittapi/src/ittnotify/ittnotify_static.c:66:37: warning: "__INTEL_COMPILER" is not defined, evaluates to 0 [-Wundef]
   66 | #elif HAS_GNU_ATTR(fallthrough) && !__INTEL_COMPILER
      |                                     ^~~~~~~~~~~~~~~~

So I suggest also resolve the 3rd Wundef hit for __INTEL_COMPILER marco in my commit

[dzarukin]

Thank you for the rapid support and taking care of the last hit. It seemed to me it was addressed but looks like I missed it.