Merge "Use -language-version 1.9 in the kotlinKythe build rule" into main

java/config/kotlin.go

@@ -50,4 +50,11 @@ func init() {
 	}, " "))
 
 	pctx.StaticVariable("KotlincGlobalFlags", strings.Join([]string{}, " "))
+	// Use KotlincKytheGlobalFlags to prevent kotlinc version skew issues between android and
+	// g3 kythe indexers.
+	// This is necessary because there might be instances of kotlin code in android
+	// platform that are not fully compatible with the kotlinc used in g3 kythe indexers.
+	// e.g. uninitialized variables are a warning in 1.*, but an error in 2.*
+	// https://github.com/JetBrains/kotlin/blob/master/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt#L748
+	pctx.StaticVariable("KotlincKytheGlobalFlags", strings.Join([]string{"-language-version 1.9"}, " "))
 }