Dropping the SemIR dump significantly decreases the size of these test
files. This is a good tradeoff since the interesting signal from these
tests is provided by `AssertSameType` not causing an error.
```
...n/check/testdata/interop/cpp/builtins.llp64.carbon | 3152 ----------------------
...in/check/testdata/interop/cpp/builtins.lp64.carbon | 3328 ------------------------
2 files changed, 0 insertions(+), 6480 deletions(-)
```
Nicholas Bishop
a465018fec