feat: static system link

Cargo.toml

@@ -17,6 +17,7 @@ repository = "https://github.com/NoXF/libwebp-sys"
 [build-dependencies]
 cc = "1"
 glob = "0.3"
+pkg-config = "0.3.27"
 
 [features]
 default = ["std", "parallel", "neon"]
@@ -25,3 +26,4 @@ parallel = ["cc/parallel"]
 neon = []                      # ARM NEON SIMD (will crash on ARM CPUs without it)
 sse41 = []                     # x64 SSE 4.1 (will crash on x86 CPUs without it)
 avx2 = []                      # x64 AVX2 (will crash on x86 CPUs without it)
+system-link = []

build.rs

@@ -1,10 +1,24 @@
 extern crate cc;
 extern crate glob;
+extern crate pkg_config;
 
 use std::env;
 use std::path::PathBuf;
 
 fn main() {
+    if cfg!(feature = "system-link") {
+        let lib_name = "libwebp";
+        let find_system_lib = pkg_config::Config::new()
+            .statik(true)
+            .probe(lib_name)
+            .is_ok();
+
+        if find_system_lib {
+            println!("cargo:rustc-link-lib=static={}", lib_name);
+            return;
+        }
+    }
+
     let manifest_dir =
         PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR"));
     let vendor = manifest_dir.join("vendor");