libgccjit was failing to set the DECL_CONTEXT of function RESULT_DECLs,
leading to them failing to be properly handled by the inlining machinery.
Fixed thusly.
gcc/jit/ChangeLog:
PR jit/103562
* jit-playback.c (gcc::jit::playback::context::new_function): Set
DECL_CONTEXT of the result_decl.