Add support for disabling features at build time

Signed-off-by: Izuru Yakumo <yakumo.izuru@chaotic.ninja>

git-svn-id: file:///srv/svn/repo/aya/trunk@87 cec141ff-132a-4243-88a5-ce187bd62f94

cmd/aya/amber.go

@@ -1,3 +1,4 @@
+//go:build !noamber
 // Render .amber files into .html
 package main
 

cmd/aya/amber_stub.go

@@ -0,0 +1,11 @@
+//go:build noamber
+package main
+
+import (
+	"errors"
+	"io"
+)
+
+func buildAmber(path string, w io.Writer, vars Vars) error {
+	return errors.New("Amber support was disabled on build-time")
+}

cmd/aya/gcss.go

@@ -1,3 +1,4 @@
+//go:build !nogcss
 // Render .gcss files into .css
 package main
 

cmd/aya/gcss_stub.go

@@ -0,0 +1,11 @@
+//go:build nogcss
+package main
+
+import (
+	"errors"
+	"io"
+)
+
+func buildGCSS(path string, w io.Writer) error {
+	return errors.New("GCSS support was disabled at build time")
+}