Add sparc-unknown-linux-gnu target

Author: glaubitz

src/tools/build-manifest/src/main.rs

@@ -86,6 +86,7 @@ static TARGETS: &'static [&'static str] = &[
     "powerpc64-unknown-linux-gnu",
     "powerpc64le-unknown-linux-gnu",
     "s390x-unknown-linux-gnu",
+    "sparc-unknown-linux-gnu",
     "sparc64-unknown-linux-gnu",
     "sparcv9-sun-solaris",
     "wasm32-unknown-emscripten",