Fix ZSTD linking with build script and clean debian/install

- Add build.rs to handle ZSTD library linking via pkg-config
- Add pkg-config as build dependency in Cargo.toml
- Clean debian/install to avoid conflicts with manual installation
- ZSTD linking now works properly for OpenSSL with ZSTD support
- Local Debian package build succeeds

Cargo.toml

@@ -49,6 +49,9 @@ widestring = "1.2.0"
 walkdir = "2.3.2"
 signal-hook-registry = "1.4.5"
 
+[build-dependencies]
+pkg-config = "0.3"
+
 [profile.release]
 # We assume we're being delivered via e.g. RPM which supports split debuginfo
 debug = true