Add use_system_unicorn feature in rust bindings

bindings/rust/Cargo.toml

@@ -24,8 +24,14 @@ bitflags = "1.3"
 libc = "0.2"
 
 [build-dependencies]
-build-helper = "0.1"
-reqwest = { version = "0.11", features = ["blocking"] }
-flate2 = "1.0.22"
-tar = "0.4.37"
-bytes = "1.1.0"
+reqwest = { optional = true, version = "0.11", features = ["blocking"] }
+flate2 = { optional = true, version = "1.0" }
+tar = { optional = true, version = "0.4" }
+bytes = { optional = true, version = "1" }
+pkg-config = { optional = true, version = "0.3" }
+
+[features]
+default = ["build_unicorn_cmake"]
+
+use_system_unicorn = ["pkg-config"]
+build_unicorn_cmake = ["reqwest", "flate2", "tar", "bytes"]

bindings/rust/build.rs

@@ -1,10 +1,19 @@
+#[cfg(feature = "build_unicorn_cmake")]
 use bytes::Buf;
+#[cfg(feature = "build_unicorn_cmake")]
 use flate2::read::GzDecoder;
+#[cfg(feature = "use_system_unicorn")]
+use pkg_config;
+#[cfg(feature = "build_unicorn_cmake")]
 use reqwest::header::USER_AGENT;
+#[cfg(feature = "build_unicorn_cmake")]
 use std::path::{Path, PathBuf};
+#[cfg(feature = "build_unicorn_cmake")]
 use std::{env, process::Command};
+#[cfg(feature = "build_unicorn_cmake")]
 use tar::Archive;
 
+#[cfg(feature = "build_unicorn_cmake")]
 fn find_unicorn(unicorn_dir: &Path) -> Option<PathBuf> {
     for entry in std::fs::read_dir(unicorn_dir).ok()? {
         let entry = entry.unwrap();
@@ -18,11 +27,13 @@ fn find_unicorn(unicorn_dir: &Path) -> Option<PathBuf> {
     None
 }
 
+#[cfg(feature = "build_unicorn_cmake")]
 fn out_dir() -> PathBuf {
     let out_dir = env::var("OUT_DIR").unwrap();
     Path::new(&out_dir).to_path_buf()
 }
 
+#[cfg(feature = "build_unicorn_cmake")]
 fn download_unicorn() -> PathBuf {
     // https://docs.github.com/en/rest/reference/repos#download-a-repository-archive-tar
     let pkg_version;
@@ -51,8 +62,9 @@ fn download_unicorn() -> PathBuf {
     find_unicorn(&out_dir).unwrap()
 }
 
+#[cfg(feature = "build_unicorn_cmake")]
 #[allow(clippy::branches_sharing_code)]
-fn main() {
+fn build_with_cmake() {
     let profile = env::var("PROFILE").unwrap();
 
     if let Some(unicorn_dir) = find_unicorn(&out_dir()) {
@@ -184,3 +196,16 @@ fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=src");
 }
+
+fn main() {
+    if cfg!(feature = "use_system_unicorn") {
+        #[cfg(feature = "use_system_unicorn")]
+        pkg_config::Config::new()
+            .atleast_version("2")
+            .probe("unicorn")
+            .expect("Could not find system unicorn2");
+    } else {
+        #[cfg(feature = "build_unicorn_cmake")]
+        build_with_cmake();
+    }
+}