Support building mixed versions of sepolicy

Now newer system policy and older vendor policy can be built together by
setting following variables:

- BOARD_SEPOLICY_VERS
- BOARD_REQD_MASK_POLICY (copy of older system/sepolicy/reqd_mask)
- BOARD_PLAT_VENDOR_POLICY (copy of older system/sepolicy/vendor)
- BOARD_(SYSTEM_EXT|PRODUCT)_(PUBLIC|PRIVATE)_PREBUILT_DIRS (copy of
  older system_ext and product policies)

Bug: 168159977
Test: try normal build and mixed build
Test: boot and check selinux denials
Change-Id: Ie239580433ffd293fa6891cd665fb5ef83c0a14f
diff --git a/build/soong/filegroup.go b/build/soong/filegroup.go
index 63873d2..700f8e0 100644
--- a/build/soong/filegroup.go
+++ b/build/soong/filegroup.go
@@ -55,8 +55,9 @@
 	productPublicSrcs  android.Paths
 	productPrivateSrcs android.Paths
 
-	vendorSrcs android.Paths
-	odmSrcs    android.Paths
+	vendorSrcs         android.Paths
+	vendorReqdMaskSrcs android.Paths
+	odmSrcs            android.Paths
 }
 
 // Source files from system/sepolicy/public
@@ -104,6 +105,10 @@
 	return fg.vendorSrcs
 }
 
+func (fg *fileGroup) VendorReqdMaskSrcs() android.Paths {
+	return fg.vendorReqdMaskSrcs
+}
+
 // Source files from BOARD_ODM_SEPOLICY_DIRS
 func (fg *fileGroup) OdmSrcs() android.Paths {
 	return fg.odmSrcs
@@ -141,6 +146,7 @@
 	fg.productPublicSrcs = fg.findSrcsInDirs(ctx, ctx.Config().ProductPublicSepolicyDirs())
 	fg.productPrivateSrcs = fg.findSrcsInDirs(ctx, ctx.Config().ProductPrivateSepolicyDirs())
 
+	fg.vendorReqdMaskSrcs = fg.findSrcsInDirs(ctx, ctx.DeviceConfig().BoardReqdMaskPolicy())
 	fg.vendorSrcs = fg.findSrcsInDirs(ctx, ctx.DeviceConfig().VendorSepolicyDirs())
 	fg.odmSrcs = fg.findSrcsInDirs(ctx, ctx.DeviceConfig().OdmSepolicyDirs())
 }
diff --git a/build/soong/selinux_contexts.go b/build/soong/selinux_contexts.go
index 8e2d1da..a2dad9b 100644
--- a/build/soong/selinux_contexts.go
+++ b/build/soong/selinux_contexts.go
@@ -158,7 +158,9 @@
 		if ctx.ProductSpecific() {
 			inputs = append(inputs, segroup.ProductPrivateSrcs()...)
 		} else if ctx.SocSpecific() {
-			inputs = append(inputs, segroup.SystemVendorSrcs()...)
+			if ctx.DeviceConfig().BoardSepolicyVers() == ctx.DeviceConfig().PlatformSepolicyVersion() {
+				inputs = append(inputs, segroup.SystemVendorSrcs()...)
+			}
 			inputs = append(inputs, segroup.VendorSrcs()...)
 		} else if ctx.DeviceSpecific() {
 			inputs = append(inputs, segroup.OdmSrcs()...)
@@ -170,7 +172,11 @@
 		}
 
 		if proptools.Bool(m.properties.Reqd_mask) {
-			inputs = append(inputs, segroup.SystemReqdMaskSrcs()...)
+			if ctx.SocSpecific() || ctx.DeviceSpecific() {
+				inputs = append(inputs, segroup.VendorReqdMaskSrcs()...)
+			} else {
+				inputs = append(inputs, segroup.SystemReqdMaskSrcs()...)
+			}
 		}
 	})