[Bug jit/64089] libgccjit.so.0.0.1 linkage failure on darwin

[howarth at bromo dot med.uc.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64089

--- Comment #3 from howarth at bromo dot med.uc.edu ---
Note that on darwin libgcc handles its symbol map using...

 -Wl,-exported_symbols_list,$(SHLIB_MAP) 

on SHLIB_LINK.