fix(nvm): don't use local npm version when getting the bin

no issue
- pass {preferLocal: true} to the `npm bin -g` execa command so that the npm version located by the CLI is the same as the one the user normally uses

Author: acburdine

lib/commands/doctor/checks/install.js

@@ -37,7 +37,7 @@ const tasks = {
         });
     },
     nodeVersion: function nodeVersion(ctx) {
-        let globalBin = execa.shellSync('npm bin -g').stdout;
+        let globalBin = execa.shellSync('npm bin -g', {preferLocal: false}).stdout;
 
         if (process.argv[1] !== path.join(__dirname, '../../../../bin/ghost') && !process.argv[1].startsWith(globalBin)) {
             return Promise.reject(new errors.SystemError(

test/unit/commands/doctor/install-spec.js

@@ -52,7 +52,7 @@ describe('Unit: Doctor Checks > Install', function () {
                 expect(error).to.be.an.instanceof(errors.SystemError);
                 expect(error.message).to.match(/version of Ghost-CLI you are running was not installed with this version of Node./);
                 expect(execaStub.calledOnce).to.be.true;
-                expect(execaStub.calledWithExactly('npm bin -g')).to.be.true;
+                expect(execaStub.calledWithExactly('npm bin -g', {preferLocal: false})).to.be.true;
             });
         });