It seems that flang expects this to work. Even though long isn't
i32 on RV64 or most X86-64 platforms.
It's easy for us to support when we have native FP instructions.
I fell back to i64 and truncated the result otherwise. The
documentation for lround says it returns an unspecified value if
doesn't fit in the integer type. I have no idea what flang is
expecting. I really only did the libcall to avoid forking a test.