Support target s390x-unknown-linux-musl (#97)

Author: messense

src/lib.rs

@@ -262,6 +262,7 @@ impl Build {
             "powerpc64le-unknown-linux-musl" => "linux-ppc64le",
             "riscv64gc-unknown-linux-gnu" => "linux-generic64",
             "s390x-unknown-linux-gnu" => "linux64-s390x",
+            "s390x-unknown-linux-musl" => "linux64-s390x",
             "x86_64-apple-darwin" => "darwin64-x86_64-cc",
             "x86_64-linux-android" => "linux-x86_64",
             "x86_64-pc-windows-gnu" => "mingw64",