We hit some undefined symbol errors to 128-bit floating point functions when linking this test.
```
ld.lld: error: undefined symbol: __multf3
>>> referenced by strtof128_l.o:(round_and_return) in archive /usr/lib/x86_64-linux-gnu/libc.a
>>> referenced by strtof128_l.o:(round_and_return) in archive /usr/lib/x86_64-linux-gnu/libc.a
>>> referenced by strtof128_l.o:(round_and_return) in archive /usr/lib/x86_64-linux-gnu/libc.a
>>> referenced 4 more times
>>> did you mean: __muldf3
>>> defined in: /usr/local/google/home/leonardchan/llvm-monorepo/llvm-build-1-master-fuchsia-toolchain/lib/clang/14.0.0/lib/x86_64-unknown-linux-gnu/libclang_rt.builtins.a
```
Host libc expects these to be defined, and compiler-rt will only define these for certain platforms (see definition for `CRT_HAS_128BIT`). Since we likely can't do anything about the host libc, we can at least restrict the test to check that 128-bit types are supported.