fix mzschemecgc name (to not overwrite mzscheme)

collects/mzscheme/installer.ss

@@ -6,6 +6,7 @@
 (define (post-installer path)
   (define variants (available-mzscheme-variants))
   (for ([v (in-list variants)])
+    (parameterize ([current-launcher-variant v])
       (create-embedding-executable	 
        (mzscheme-program-launcher-path "MzScheme")
        #:variant v
@@ -13,4 +14,4 @@
        #:launcher? #t
        #:aux '((framework-root . #f)
                (dll-dir . #f)
-             (relative? . #t)))))
+               (relative? . #t))))))