Distinguish the intent of PackagingSpec

A PackagingSpec actually means either of two: an installation of a file
(i.e. putting the file on a filesystem image), or a simple gathering.
However, so far, the two different intents was not visible in
PackagingSpecs returns from TransitivePackagingSpecs().

With this change, the two different intents are recorded in
PackagingSpec. A PackagingSpec has a boolean field which records the
value of the SkipInstall() of the module where the PackagingSpec was
created from.

This could be used by a module like android_system_image which wants to
follow the "installation" semantic. For example, the module type doesn't
want to include a stub variant of a shared lib.

This change doesn't make use of the new field, yet.

Bug: 335506668
Test: go test ./...
Change-Id: If0106642a11ba804630df79b4c5ebd608a77a6b1

android/packaging.go

@@ -43,6 +43,11 @@ type PackagingSpec struct {
 	effectiveLicenseFiles *Paths
 
 	partition string
+
+	// Whether this packaging spec represents an installation of the srcPath (i.e. this struct
+	// is created via InstallFile or InstallSymlink) or a simple packaging (i.e. created via
+	// PackageFile).
+	skipInstall bool
 }
 
 // Get file name of installed package
@@ -74,6 +79,10 @@ func (p *PackagingSpec) Partition() string {
 	return p.partition
 }
 
+func (p *PackagingSpec) SkipInstall() bool {
+	return p.skipInstall
+}
+
 type PackageModule interface {
 	Module
 	packagingBase() *PackagingBase