Give compliance a pkgPath

Change the pkgPath of compliance to android/soong/tools/compliance
to distinguish it from the standard library.

Also add a go.mod file so that the Go tools can find the package.

Test: go test ./...
Change-Id: I061be2b91378db6508e9c88be2548648af8be4e7
diff --git a/tools/compliance/cmd/bom.go b/tools/compliance/cmd/bom.go
index ec01603..aaec786 100644
--- a/tools/compliance/cmd/bom.go
+++ b/tools/compliance/cmd/bom.go
@@ -16,7 +16,6 @@
 
 import (
 	"bytes"
-	"compliance"
 	"flag"
 	"fmt"
 	"io"
@@ -24,6 +23,8 @@
 	"os"
 	"path/filepath"
 	"strings"
+
+	"android/soong/tools/compliance"
 )
 
 var (