install: update install.js to use `process.config`

Now that the node_prefix is available from within node, we can use it :)

Makefile

@@ -33,10 +33,10 @@ out/Makefile: common.gypi deps/uv/uv.gyp deps/http_parser/http_parser.gyp deps/z
 	tools/gyp_node -f make
 
 install: all
-	out/Release/node tools/installer.js ./config.gypi install
+	out/Release/node tools/installer.js install
 
 uninstall:
-	out/Release/node tools/installer.js ./config.gypi uninstall
+	out/Release/node tools/installer.js uninstall
 
 clean:
 	-rm -rf out/Makefile node node_g out/$(BUILDTYPE)/node

tools/installer.js

@@ -1,21 +1,15 @@
 var fs = require('fs'),
     path = require('path'),
     exec = require('child_process').exec,
-    options = fs.readFileSync(process.argv[2]).toString(),
-    cmd = process.argv[3];
+    cmd = process.argv[2];
 
 if (cmd !== 'install' && cmd !== 'uninstall') {
   console.error('Unknown command: ' + cmd);
   process.exit(1);
 }
 
-// Python pprint.pprint() uses single quotes instead of double.
-// awful.
-options = options.replace(/'/gi, '"')
-
-// Parse options file and remove first comment line
-options = JSON.parse(options.split('\n').slice(1).join(''));
-var variables = options.variables,
+// Use the built-in config reported by the current process
+var variables = process.config.variables,
     node_prefix = variables.node_prefix || '/usr/local';
 
 // Execution queue