build: expand ~ in install prefix early

The install prefix gets written to config.gypi and config.mk.  Tildes
were expanded in the first file but not in the second one, causing the
`make install` target to install files to a directory named `~` in
the current working directory.

Fixes: https://github.com/nodejs/node/issues/75
PR-URL: https://github.com/nodejs/io.js/pull/2307
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

configure

@@ -335,6 +335,9 @@ parser.add_option('--enable-static',
 
 (options, args) = parser.parse_args()
 
+# Expand ~ in the install prefix now, it gets written to multiple files.
+options.prefix = os.path.expanduser(options.prefix or '')
+
 # set up auto-download list
 auto_downloads = nodedownload.parse(options.download_list)
 
@@ -611,7 +614,7 @@ def configure_mips(o):
 def configure_node(o):
   if options.dest_os == 'android':
     o['variables']['OS'] = 'android'
-  o['variables']['node_prefix'] = os.path.expanduser(options.prefix or '')
+  o['variables']['node_prefix'] = options.prefix
   o['variables']['node_install_npm'] = b(not options.without_npm)
   o['default_configuration'] = 'Debug' if options.debug else 'Release'