Add Windows target on Windows host build option (#68)

Project can be build on windows using rust stable-x86_64-pc-windows-gnu
and msys2/Mingw64. The MINGW64_DIR environment variable becomes
mandatory and must point to the local mingw64 toolchain install.

Author: ldoguin

build.rs

@@ -172,6 +172,15 @@ fn generate_bindings() -> Result<(), Box<dyn Error>> {
             .clang_arg(format!("--target={}", "x86_64-pc-windows-gnu"));
     }
 
+    if is_host(OperatingSystem::Windows)? && is_target(OperatingSystem::Windows)? {
+        let mingw_path = env::var("MINGW64_DIR")
+            .expect("Please set MINGW64_DIR to the location of your mingw64 installation ");
+        let mingw_include_path = format!("{mingw_path}\\include");
+        bindings = bindings
+            .clang_arg(format!("-I{}", mingw_include_path))
+            .clang_arg(format!("--target={}", "x86_64-pc-windows-gnu"));
+    }
+
     let out_dir = env::var("OUT_DIR")?;
     bindings
         .allowlist_type("CBL.*")