Disable parallel builds for vim (#3893)

* Disable parallel builds

The install step creates a bunch of links to the vim binary, e.g.
`view`.  When run with -j greater than 1 there are silent failures.

Running w/out parallelism seems to fix it.

* Only constrain the install phase to be -j 1

Thanks @adamjstewart!

var/spack/repos/builtin/packages/vim/package.py

@@ -129,3 +129,9 @@ def configure_args(self):
             configure_args.append("--enable-cscope")
 
         return configure_args
+
+    # Run the install phase with -j 1.  There seems to be a problem with
+    # parallel builds that results in the creation of the links (e.g. view)
+    # to the vim binary silently failing.
+    def install(self, spec, prefix):
+        make('install', parallel=False)