skip rust-openssl-tests on sparc64

skip rust-openssl-tests on sparc64

The issue is likely that the build is trying to compile some generated
C code with the prehistoric gcc from base, so add a tentative workaround
for that. Since I don't currently have access to a sparc64 box where I
could validate this easily and check if the workaround is enough, let's
not waste lots of cycles on this.