Bug#913946: llvm*7 unstripped

[Rebecca N. Palmer]

> dh_strip uses objcopy as well as strip, so we might need to similarly force that to the LLVM version. 

That won't work: LLVM objcopy doesn't accept --compress-debug-sections, 
and accepts but ignores --only-keep-debug. 
https://sources.debian.org/src/debhelper/11.5.3/dh_strip/#L308

Also, LLVM strip doesn't accept --enable-deterministic-archives, used 
for static libraries.

> While this could be the result of dh_strip crashing, local testing 
> suggests llvm-strip --remove-section=.comment --remove-section=.note 
> --strip-unneeded [library filename] 
> *doesn't actually strip anything*.
--strip-debug makes it do something.  (dh_strip passes that for static 
libraries, but not shared ones.)  This suggests making 'strip' a 1-line 
script "llvm-strip --strip-debug $*" not just a symlink.

Also, while I do get *some* "failed to find link section" errors with 
GNU strip and these "unstripped" libraries, they aren't the same ones as 
had such an error in the old build log.  These errors do not appear with 
LLVM strip.