As described in Issue #57642, flang currently lacks SPARC support in Optimizer/CodeGen/Target.cpp, which causes a considerable number of tests to FAIL with
error: flang/lib/Optimizer/CodeGen/Target.cpp:310: not yet implemented: target not implemented
This patch fixes this by following GCC`s documentation of the ABI described in the Issue.
Tested on sparcv9-sun-solaris2.11.
I'm not fully certain I've done this correctly, so extra scrutiny would be most welcome. Besides, I wonder why flang has to do this at all (and for complex values only) since the SPARC backend knows how to handle complex args and return values just fine.
Nit: It would be nice to also test a Linux triple here (it can use the same check prefix as Solaris).