Fix apps build

Fix two problems with Soong's aapt2 rules that occur when
TARGET_BUILD_APPS is set.  Fix escaping the values passed to
--min-sdk-version, they are sometimes P-$$(cat out/build_number.txt).
Also use the correct path to the aapt2 prebuilt.

Bug: 69917341
Test: m TARGET_PRODUCT=full TARGET_BUILD_VARIANT=userdebug TARGET_BUILD_APPS=Camera2
Change-Id: I8660a62c4a87a74e0ac1b9d03d67103af93a0cbe
diff --git a/java/app.go b/java/app.go
index 6866e2a..ed6a9db 100644
--- a/java/app.go
+++ b/java/app.go
@@ -254,7 +254,7 @@
 	sdkVersion := String(a.deviceProperties.Sdk_version)
 	switch sdkVersion {
 	case "", "current", "system_current", "test_current":
-		sdkVersion = ctx.Config().AppsDefaultVersionName()
+		sdkVersion = proptools.NinjaEscape([]string{ctx.Config().AppsDefaultVersionName()})[0]
 	}
 
 	linkFlags = append(linkFlags, "--min-sdk-version "+sdkVersion)