Support multiple crtbegin and crtend dependencies

Musl libc with an embedded linker uses multiple crtbegin dependencies,
convert rust's CrtBegin and CrtEnd to lists.

Bug: 190084016
Test: m USE_HOST_MUSL=true host-native
Change-Id: Ie843801e87b1f38ace84502d9e4f938a92ec1fa2
diff --git a/rust/rust.go b/rust/rust.go
index cba92c3..ee573fa 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -393,7 +393,7 @@
 	DataLibs []string
 	DataBins []string
 
-	CrtBegin, CrtEnd string
+	CrtBegin, CrtEnd []string
 }
 
 type PathDeps struct {
@@ -419,8 +419,8 @@
 	depGeneratedHeaders   android.Paths
 	depSystemIncludePaths android.Paths
 
-	CrtBegin android.OptionalPath
-	CrtEnd   android.OptionalPath
+	CrtBegin android.Paths
+	CrtEnd   android.Paths
 
 	// Paths to generated source files
 	SrcDeps          android.Paths
@@ -1214,9 +1214,9 @@
 				depPaths.depSystemIncludePaths = append(depPaths.depSystemIncludePaths, exportedInfo.SystemIncludeDirs...)
 				depPaths.depGeneratedHeaders = append(depPaths.depGeneratedHeaders, exportedInfo.GeneratedHeaders...)
 			case depTag == cc.CrtBeginDepTag:
-				depPaths.CrtBegin = linkObject
+				depPaths.CrtBegin = append(depPaths.CrtBegin, linkObject.Path())
 			case depTag == cc.CrtEndDepTag:
-				depPaths.CrtEnd = linkObject
+				depPaths.CrtEnd = append(depPaths.CrtEnd, linkObject.Path())
 			}
 
 			// Make sure these dependencies are propagated
@@ -1422,13 +1422,13 @@
 	actx.AddVariationDependencies(nil, cc.HeaderDepTag(), deps.HeaderLibs...)
 
 	crtVariations := cc.GetCrtVariations(ctx, mod)
-	if deps.CrtBegin != "" {
+	for _, crt := range deps.CrtBegin {
 		actx.AddVariationDependencies(crtVariations, cc.CrtBeginDepTag,
-			cc.RewriteSnapshotLib(deps.CrtBegin, cc.GetSnapshot(mod, &snapshotInfo, actx).Objects))
+			cc.RewriteSnapshotLib(crt, cc.GetSnapshot(mod, &snapshotInfo, actx).Objects))
 	}
-	if deps.CrtEnd != "" {
+	for _, crt := range deps.CrtEnd {
 		actx.AddVariationDependencies(crtVariations, cc.CrtEndDepTag,
-			cc.RewriteSnapshotLib(deps.CrtEnd, cc.GetSnapshot(mod, &snapshotInfo, actx).Objects))
+			cc.RewriteSnapshotLib(crt, cc.GetSnapshot(mod, &snapshotInfo, actx).Objects))
 	}
 
 	if mod.sourceProvider != nil {