Add cargo:ROOT output for library paths

Author: jkawamoto

openblas-src/build.rs

@@ -42,6 +42,7 @@ fn windows_gnu_system() {
     )
     .expect("cygpath output includes non UTF-8 string");
     println!("cargo:rustc-link-search={}", lib_path);
+    println!("cargo:ROOT={}",lib_path);
 }
 
 /// Use vcpkg for msvc "system" feature
@@ -75,6 +76,7 @@ fn macos_system() {
 
     println!("cargo:rustc-link-search={}/lib", openblas.display());
     println!("cargo:rustc-link-search={}/lib", libomp.display());
+    println!("cargo:ROOT={}", openblas.display());
 }
 
 fn main() {
@@ -220,6 +222,7 @@ fn build() {
     };
 
     println!("cargo:rustc-link-search={}", source.display());
+    println!("cargo:ROOT={}", source.display());
     for search_path in &make_conf.c_extra_libs.search_paths {
         println!("cargo:rustc-link-search={}", search_path.display());
     }