Update SDL; add no-link feature

Cargo.toml

@@ -55,6 +55,7 @@ use-vcpkg = ["sdl2-sys/use-vcpkg"]
 use_mac_framework = ["sdl2-sys/use_mac_framework"]
 bundled = ["sdl2-sys/bundled"]
 static-link = ["sdl2-sys/static-link"]
+no-link = ["sdl2-sys/no-link"]
 
 [package.metadata.docs.rs]
 features = ["default", "gfx", "mixer", "image", "ttf"]

sdl2-sys/Cargo.toml

@@ -50,6 +50,7 @@ use-pkgconfig = ["pkg-config"]
 use-vcpkg = ["vcpkg"]
 use-bindgen = ["bindgen"]
 static-link = []
+no-link = []
 use_mac_framework = []
 bundled = ["cmake"]
 mixer = []

sdl2-sys/build.rs

@@ -495,6 +495,7 @@ fn main() {
         println!("cargo:include={}", sdl2_includes);
     }
 
+    #[cfg(not(feature = "no-link"))]
     link_sdl2(target_os);
 
     // Android builds shared libhidapi.so even for static builds.