Build failure on Windows since OCL_ICD_ENABLE_TRACE addition

[BtbN]

Hi!

Since the new environment variable was added, building the loader for Windows fails with the following error:

/stage/opencl/loader/loader/windows/icd_windows_apppackage.cpp:23:9: error: conflicting declaration of 'int khrEnableTrace' with 'C' linkage
   23 |     int khrEnableTrace;
      |         ^~~~~~~~~~~~~~
In file included from /stage/opencl/loader/loader/windows/icd_windows_apppackage.cpp:19:
/stage/opencl/loader/loader/icd.h:87:12: note: previous declaration with 'C++' linkage
   87 | extern int khrEnableTrace;
      |            ^~~~~~~~~~~~~~
make[2]: *** [CMakeFiles/OpenCL.dir/build.make:181: CMakeFiles/OpenCL.dir/loader/windows/icd_windows_apppackage.cpp.obj] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [CMakeFiles/Makefile2:95: CMakeFiles/OpenCL.dir/all] Error 2
make: *** [Makefile:149: all] Error 2

Not entirely sure what the correct fix for this is. Maybe the header-include also needs wrapped in extern "C"?

[cdai2]

#171 is to fix this issue.
Sorry that this compilation error is not exposed on my local machine before.

[cdai2]

As #171 is landed. Please verify and close this issue. @BtbN

[BtbN]

Yep, all builds succeeded!