Add support for install-strip target

[uilianries]

Hello!

The GNU standard targets point to install-strip as a known target, where it invokes strip in order to remove symbols from binaries.

As the libpcap is heavily used in memory-constrained embedded environments, allowing an immediate stripped install helps the creation of lightweight root filesystems, like when using Buildroot or Yocto. For a regular Desktop application, it can still remove debug symbols.

I built locally on Linux to validate this new target: libpcap-1.11.0-linux-amd64-gcc13-release-shared-stripped.log

Steps to Reproduce

mkdir build && cd build/
autoreconf --install --force --verbose .. 
../configure --prefix=/tmp/install --enable-shared
make
make install-strip
file /tmp/install/lib/libpcap.so.1.11.0-PRE-GIT

Regards!

[infrastation]

strip allows to specify more than one file argument, so with this approach there is no need to have three separate invocation.

Alternatively, since the "install-shared" target is parametrised on DYEXT, it could make more sense to parametrise "install-strip" the same way, then strip would apply to exactly the files that have been just installed.

On a separate note, this change does not strip rpcapd.

[infrastation]

There are sound reasons to strip installed binaries, but as far as I am aware, various Linux and BSD distributions already enforce this directly and skip a dependency on "install-strip". That is, after "make install" has populated a temporary directory with files, but before all/some contents of the temporary directory becomes contents of a package, a distribution-specific script identifies and strips all binaries. This practice originates in times when the entire OS had to fit on a single CD, and before that — on as few floppies as possible.