Calling NPM without the user's shell profile.

According to the NPM man page, npm gets its configuration information from 5 separate sources. When npm is launched on a *nix system without the user shell npm skips any configuration in the user's $HOME as well as ignores environment variables that might be set in the user's profile or environment.

This resolves appium#1889 and @ZuhayrMerchant110's issue as well as mine where the project directory prefixing the appium path.

src/main/java/io/appium/java_client/service/local/AppiumServiceBuilder.java

@@ -147,7 +147,8 @@ private static File findMainScript() {
         List<String> cmdLine = System.getProperty("os.name").toLowerCase().contains("win")
                 // npm is a batch script, so on windows we need to use cmd.exe in order to execute it
                 ? Arrays.asList("cmd.exe", "/c", String.format("\"%s\" root -g", npm.getAbsolutePath()))
-                : Arrays.asList(npm.getAbsolutePath(), "root", "-g");
+                //ProcessBuilder doesn't execute a shell, some npm functionality requires the user's shell profile
+                : Arrays.asList("/bin/sh", "--login", "-c", npm.getAbsolutePath() + " root -g");
         ProcessBuilder pb = new ProcessBuilder(cmdLine);
         String nodeModulesRoot;
         try {