Set LINKFLAGS env var

The waf build uses LINKFLAGS not LDFLAGS. Set
LINKFLAGS the same as LDFLAGS so the build can
find libraries from a non-/usr/local brew install

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/jack.rb

@@ -14,8 +14,9 @@ class Jack <Formula
   end
 
   def install
-    system "./waf configure --prefix=#{prefix}"
-    system "./waf build"
-    system "./waf install"
+    ENV['LINKFLAGS'] = ENV['LDFLAGS']
+    system "./waf","configure","--prefix=#{prefix}"
+    system "./waf","build"
+    system "./waf","install"
   end
 end