Make glslang work on Linux

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "glsl-to-spirv/glslang"]
+	path = glsl-to-spirv/glslang
+	url = https://github.com/KhronosGroup/glslang

glsl-to-spirv/Cargo.toml

@@ -6,3 +6,6 @@ build = "build/build.rs"
 
 [dependencies]
 tempdir = "0.3.4"
+
+[build-dependencies]
+cmake = "0.1.13"

glsl-to-spirv/build/build.rs

@@ -1,38 +1,25 @@
+extern crate cmake;
+
 use std::env;
 use std::fs;
-use std::fs::Permissions;
 use std::path::Path;
 
 fn main() {
-    println!("cargo:rerun-if-changed=build/glslangValidator");
     println!("cargo:rerun-if-changed=build/glslangValidator.exe");
 
     let target = env::var("TARGET").unwrap();
     let out_file = Path::new(&env::var("OUT_DIR").unwrap()).join("glslang_validator");
 
     let path = if target.contains("windows") {
-        Path::new("build/glslangValidator.exe")
-    } else if target.contains("linux") {
-        Path::new("build/glslangValidator")
+        // TODO: check the hash of the file to make sure that it is not altered
+        Path::new("build/glslangValidator.exe").to_owned()
     } else {
-        panic!("The platform `{}` is not supported", target);
+        // TODO: automatically initialize the submodule if it wasn't done
+        cmake::build("glslang");
+        Path::new(&env::var("OUT_DIR").unwrap()).join("bin").join("glslangValidator")
     };
 
     if let Err(_) = fs::hard_link(&path, &out_file) {
         fs::copy(&path, &out_file).expect("failed to copy executable");
     }
-
-    // TODO: check the hash of the files to make sure that they are not altered
-
-    // setting permissions of the executable
-    {
-        #[cfg(unix)] fn permissions() -> Option<Permissions> {
-            use std::os::unix::fs::PermissionsExt;
-            Some(Permissions::from_mode(755))
-        }
-        #[cfg(not(unix))] fn permissions() -> Option<Permissions> { None }
-        if let Some(permissions) = permissions() {
-            fs::set_permissions(&out_file, permissions).expect("failed to set permissions");
-        }
-    }
 }

glsl-to-spirv/glslang

@@ -0,0 +1 @@
+Subproject commit 5047c6f7a70924bfac38c2c9e487299b3416a7f9