This reverts commit 40333cde2b.
The implementation is buggy. There are thousands of failures in
```
FILECHECK_OPTS=--diff ninja -C /tmp/Rel check-llvm-mc
FILECHECK_OPTS=--diff ninja -C /tmp/Rel check-lld-elf
```
This reverts commit 40333cde2b.
The implementation is buggy. There are thousands of failures in
```
FILECHECK_OPTS=--diff ninja -C /tmp/Rel check-llvm-mc
FILECHECK_OPTS=--diff ninja -C /tmp/Rel check-lld-elf
```