package/apitrace: disable unit tests

package/apitrace: disable unit tests

This will avoid the following build failure with xtensa:

[ 62%] Linking CXX executable ../../guids_test
[ 62%] Building CXX object retrace/CMakeFiles/retrace_common.dir/retrace.cpp.o
CMakeFiles/guids_test.dir/guids_test.cpp.o:(.debug_line+0xf7b): dangerous relocation: overflow after relaxation
collect2: error: ld returned 1 exit status
lib/guids/CMakeFiles/guids_test.dir/build.make:85: recipe for target 'guids_test' failed

Fixes:
 - http://autobuild.buildroot.org/results/8fea93a88bb34e98e391a048c3b996b45ebac803

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>