Sort imports of durable code for output stability (#133)

It avoids sometimes getting unexpected diffs when re-compiling the same
program on a different machine.

compiler/compile.go

@@ -1,6 +1,7 @@
 package compiler
 
 import (
+	"cmp"
 	"fmt"
 	"go/ast"
 	"go/build/constraint"
@@ -402,6 +403,12 @@ func addImports(p *packages.Package, gen *ast.File) *ast.File {
 		})
 	}
 
+	// Imports don't require to be sorted but it helps with output
+	// stability. The format pass does not take care of this.
+	slices.SortFunc(importspecs, func(a, b ast.Spec) int {
+		return cmp.Compare(a.(*ast.ImportSpec).Name.Name, b.(*ast.ImportSpec).Name.Name)
+	})
+
 	gen.Decls = append([]ast.Decl{&ast.GenDecl{
 		Tok:   token.IMPORT,
 		Specs: importspecs,