Support OUT_DIR for license graph.

Bug: 226066987

Test: OUT_DIR=/tmp/outdir m all listshare checkshare htmlnotice rtrace dumpgraph dumpresolutions compliancenotice_bom compliancenotice_shippedlibs
Test: OUT_DIR=/tmp/outdir m /tmp/outdir/target/product/bonito/obj/NOTICE.xml.gz
Test: m all listshare checkshare htmlnotice rtrace dumpgraph dumpresolutions compliancenotice_bom compliancenotice_shippedlibs
Test: m out/target/product/bonito/obj/NOTICE.xml.gz

Change-Id: I6282c647a389c5935d5ce7c79193f86d32c76365

tools/compliance/readgraph.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"os"
 	"strings"
 	"sync"
 
@@ -31,6 +32,22 @@ var (
 	ConcurrentReaders = 5
 )
 
+type globalFS struct{}
+
+func (s globalFS) Open(name string) (fs.File, error) {
+	return os.Open(name)
+}
+
+var FS globalFS
+
+// GetFS returns a filesystem for accessing files under the OUT_DIR environment variable.
+func GetFS(outDir string) fs.FS {
+	if len(outDir) > 0 {
+		return os.DirFS(outDir)
+	}
+	return os.DirFS(".")
+}
+
 // result describes the outcome of reading and parsing a single license metadata file.
 type result struct {
 	// file identifies the path to the license metadata file