compiletest: detect nodejs binary, allow override

Rather than hardcoding the binary name for running asmjs tests, attempt
to detect the name that should be used; either `nodejs` or `node`. Also
add a command-line argument to manually specify what should be used,
suppressing probing.

Fixes rust-lang#34188.

src/tools/compiletest/src/common.rs

@@ -160,6 +160,9 @@ pub struct Config {
     // status whether android device available or not
     pub adb_device_status: bool,
 
+    // Name with which to invoke Node for asmjs targets
+    pub node_path: Option<String>,
+
     // the path containing LLDB's Python module
     pub lldb_python_dir: Option<String>,
 

src/tools/compiletest/src/main.rs

@@ -102,6 +102,7 @@ pub fn parse_config(args: Vec<String> ) -> Config {
           optopt("", "android-cross-path", "Android NDK standalone path", "PATH"),
           optopt("", "adb-path", "path to the android debugger", "PATH"),
           optopt("", "adb-test-dir", "path to tests for the android debugger", "PATH"),
+          optopt("", "nodejs-executable", "path to Node executable for asmjs tests", "PROGRAM"),
           optopt("", "lldb-python-dir", "directory containing LLDB's python module", "PATH"),
           reqopt("", "cc", "path to a C compiler", "PATH"),
           reqopt("", "cxx", "path to a C++ compiler", "PATH"),
@@ -179,6 +180,7 @@ pub fn parse_config(args: Vec<String> ) -> Config {
             opt_str2(matches.opt_str("target")).contains("android") &&
             "(none)" != opt_str2(matches.opt_str("adb-test-dir")) &&
             !opt_str2(matches.opt_str("adb-test-dir")).is_empty(),
+        node_path: matches.opt_str("nodejs-executable").or_else(detect_node),
         lldb_python_dir: matches.opt_str("lldb-python-dir"),
         verbose: matches.opt_present("verbose"),
         quiet: matches.opt_present("quiet"),
@@ -524,3 +526,24 @@ fn extract_lldb_version(full_version_line: Option<String>) -> Option<String> {
     }
     None
 }
+
+fn detect_node() -> Option<String> {
+    // Look for `nodejs` or `node` on PATH in that order, returning the name
+    // of whichever is found.
+    let path = match env::var_os("PATH") {
+        Some(x) => x,
+        None => return None
+    };
+
+    for mut dir in env::split_paths(&path) {
+        for bin in &["nodejs", "node"] {
+            dir.push(bin);
+            if dir.exists() {
+                return Some(bin.to_string());
+            }
+            dir.pop();
+        }
+    }
+    None
+}
+

src/tools/compiletest/src/runtest.rs

@@ -1405,7 +1405,11 @@ actual:\n\
 
         // If this is emscripten, then run tests under nodejs
         if self.config.target == "asmjs-unknown-emscripten" {
-            args.push("nodejs".to_owned());
+            if let Some(ref p) = self.config.node_path {
+                args.push(p.clone());
+            } else {
+                self.fatal("no Node binary found (--nodejs-executable)");
+            }
         }
 
         let exe_file = self.make_exe_name();