Reverts d43df749ac
NetBSD makefiles strip local symbols from libs using `OBJCOPY?=objcopy`,
which is missing on macOS. GNU objcopy appears to succeed but produces
broken .a libs which do not link into dependers.
(As this issue does not fail the netbsd.compat build,
downstream netbsd.install is added to passthru.tests.)
Since `OBJCOPY` is only used for stripping, we can:
* skip stripping with the hacky `OBJCOPY=echo`
* use cctools strip, which is invoked in the same way
The latter is obviously preferable if it works.
Indeed, locals are stripped, although it doesn't affect size much.
Comparison:
`OBJCOPY=echo`:
```
$ du -b result/lib/*.a
347784 result/lib/libnbcompat.a
357120 result/lib/libnbcompat_p.a
```
`OBJCOPY=${cctools}/bin/strip`:
```
$ du -b result/lib/*.a
347008 result/lib/libnbcompat.a
357120 result/lib/libnbcompat_p.a
```
9eb591df10