fallback to shelljs if pwd is empty (windows issue)

lib/modules/solidity/solcW.js

@@ -32,7 +32,7 @@ class SolcW {
           if (err) {
             return done(err);
           }
-          let requirePath = utils.joinPath(process.env.PWD, location);
+          let requirePath = utils.joinPath(utils.pwd(), location);
           solcProcess.send({action: 'loadCompiler', solcLocation: requirePath});
         });
 

lib/utils/utils.js

@@ -123,6 +123,10 @@ function proposeAlternative(word, _dictionary, _exceptions) {
   return propose(word, dictionary, {threshold: 0.3});
 }
 
+function pwd() {
+  return process.env.PWD || shelljs.pwd();
+}
+
 module.exports = {
   joinPath: joinPath,
   filesMatchingPattern: filesMatchingPattern,
@@ -138,5 +142,6 @@ module.exports = {
   exit: exit,
   downloadFile: downloadFile,
   extractTar: extractTar,
-  proposeAlternative: proposeAlternative
+  proposeAlternative: proposeAlternative,
+  pwd: pwd
 };