Regularize command-line flags.

All the notice binaries have -title

All the binaries that can -stripPrefix can strip multiple.

Bug: 68860345
Bug: 151177513
Bug: 151953481
Bug: 213388645
Bug: 210912771

Test: m all
Test: m systemlicense
Test: m bom; out/soong/host/linux-x85/bom ...
Test: m dumpgraph; out/soong/host/linux-x85/dumpgraph ...
Test: m dumpresolutions; out/soong/host/linux-x85/dumpresolutions ...
Test: m htmlnotice; out/soong/host/linux-x85/htmlnotice ...
Test: m rtrace; out/soong/host/linux-x85/rtrace ...
Test: m textnotice; out/soong/host/linux-x85/textnotice ...
Test: m xmlnotice; out/soong/host/linux-x85/xmlnotice ...

where ... is the path to the .meta_lic file for the system image. In my
case if

$ export PRODUCT=$(realpath $ANDROID_PRODUCT_OUT --relative-to=$PWD)

... can be expressed as:

${PRODUCT}/gen/META/lic_intermediates/${PRODUCT}/system.img.meta_lic

Change-Id: I08357bf1adb048abba6563cf3cea6ee6d60405e0
diff --git a/tools/compliance/cmd/bom/bom.go b/tools/compliance/cmd/bom/bom.go
index aaec786..5363a59 100644
--- a/tools/compliance/cmd/bom/bom.go
+++ b/tools/compliance/cmd/bom/bom.go
@@ -29,7 +29,7 @@
 
 var (
 	outputFile  = flag.String("o", "-", "Where to write the bill of materials. (default stdout)")
-	stripPrefix = flag.String("strip_prefix", "", "Prefix to remove from paths. i.e. path to root")
+	stripPrefix = newMultiString("strip_prefix", "Prefix to remove from paths. i.e. path to root (multiple allowed)")
 
 	failNoneRequested = fmt.Errorf("\nNo license metadata files requested")
 	failNoLicenses    = fmt.Errorf("No licenses found")
@@ -39,7 +39,20 @@
 	stdout      io.Writer
 	stderr      io.Writer
 	rootFS      fs.FS
-	stripPrefix string
+	stripPrefix []string
+}
+
+func (ctx context) strip(installPath string) string {
+	for _, prefix := range ctx.stripPrefix {
+		if strings.HasPrefix(installPath, prefix) {
+			p := strings.TrimPrefix(installPath, prefix)
+			if 0 == len(p) {
+				continue
+			}
+			return p
+		}
+	}
+	return installPath
 }
 
 func init() {
@@ -54,6 +67,19 @@
 	}
 }
 
+// newMultiString creates a flag that allows multiple values in an array.
+func newMultiString(name, usage string) *multiString {
+	var f multiString
+	flag.Var(&f, name, usage)
+	return &f
+}
+
+// multiString implements the flag `Value` interface for multiple strings.
+type multiString []string
+
+func (ms *multiString) String() string     { return strings.Join(*ms, ", ") }
+func (ms *multiString) Set(s string) error { *ms = append(*ms, s); return nil }
+
 func main() {
 	flag.Parse()
 
@@ -135,11 +161,7 @@
 	}
 
 	for path := range ni.InstallPaths() {
-		if 0 < len(ctx.stripPrefix) && strings.HasPrefix(path, ctx.stripPrefix) {
-			fmt.Fprintln(ctx.stdout, path[len(ctx.stripPrefix):])
-		} else {
-			fmt.Fprintln(ctx.stdout, path)
-		}
+		fmt.Fprintln(ctx.stdout, ctx.strip(path))
 	}
 	return nil
 }
diff --git a/tools/compliance/cmd/bom/bom_test.go b/tools/compliance/cmd/bom/bom_test.go
index 163ac2a..4a9889f 100644
--- a/tools/compliance/cmd/bom/bom_test.go
+++ b/tools/compliance/cmd/bom/bom_test.go
@@ -282,7 +282,7 @@
 				rootFiles = append(rootFiles, "testdata/"+tt.condition+"/"+r)
 			}
 
-			ctx := context{stdout, stderr, os.DirFS("."), tt.stripPrefix}
+			ctx := context{stdout, stderr, os.DirFS("."), []string{tt.stripPrefix}}
 
 			err := billOfMaterials(&ctx, rootFiles...)
 			if err != nil {