Add experimental option to target Java 17

Bug: 233029164
Test: EXPERIMENTAL_TARGET_JAVA_VERSION_17=true \
      EXPERIMENTAL_USE_OPENJDK17_TOOLCHAIN=true m
Change-Id: I80a9ba9eb356a460c1036e711e793c2ca6620f53
diff --git a/android/config.go b/android/config.go
index 403999d..eb01baa 100644
--- a/android/config.go
+++ b/android/config.go
@@ -698,6 +698,10 @@
 	return value == "0" || value == "n" || value == "no" || value == "off" || value == "false"
 }
 
+func (c *config) TargetsJava17() bool {
+	return c.IsEnvTrue("EXPERIMENTAL_TARGET_JAVA_VERSION_17")
+}
+
 // EnvDeps returns the environment variables this build depends on. The first
 // call to this function blocks future reads from the environment.
 func (c *config) EnvDeps() map[string]string {