comp: reinstate -fcompiler-rt when used with build-obj as output
When the following is specified
```
$ zig build-obj -fcompiler-rt example.zig
```
the resulting relocatable object file will have the compiler-rt
unconditionally embedded inside.
```
$ nm example.o
...
0000000012345678 W __truncsfhf2
...
```
4e6f21e2cbJakub Konka committed on 2/14/2023, 5:12:22 PM· committed by Andrew Kelleyparent47e14b7