tests: bitcode: add missing b_bitcode option
The bitcode test did not actually have bitcode enabled,
making it not really useful.
-project('bitcode test', 'c', 'objc', 'objcpp')
+project('bitcode test', 'c', 'objc', 'objcpp',
+ default_options : ['b_bitcode=true'])
both_libraries('alib', 'libfoo.m')
shared_module('amodule', 'libfoo.m')
