Merge "Revert "Switch to JDK 21"" into main am: bfa20d7e15 am: e93ae387e8

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2994633

Change-Id: Ibe79e815e6002c57e49794b2ebadd858dc5ccc57
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

java/config/config.go

@@ -132,7 +132,12 @@ func init() {
 		if override := ctx.Config().Getenv("OVERRIDE_JLINK_VERSION_NUMBER"); override != "" {
 			return override
 		}
-		return "21"
+		switch ctx.Config().Getenv("EXPERIMENTAL_USE_OPENJDK21_TOOLCHAIN") {
+		case "true":
+			return "21"
+		default:
+			return "17"
+		}
 	})
 
 	pctx.SourcePathVariable("JavaToolchain", "${JavaHome}/bin")