Set AnalysisFlags.explicitApiVersion in tests with API_VERSION directive

To mimic the case of user passing an explicit "-api-version" flag to
avoid API version being inferred to the version of stdlib in
dependencies by JvmRuntimeVersionsConsistencyChecker

compiler/tests-common/tests/org/jetbrains/kotlin/checkers/CompilerTestLanguageVersionSettings.kt

@@ -68,7 +68,8 @@ fun parseLanguageVersionSettings(directives: Map<String, String>): CompilerTestL
         analysisFlag(JvmAnalysisFlags.sanitizeParentheses, if (SANITIZE_PARENTHESES in directives) true else null),
         analysisFlag(AnalysisFlags.constraintSystemForOverloadResolution, directives[CONSTRAINT_SYSTEM_FOR_OVERLOAD_RESOLUTION]?.let {
             ConstraintSystemForOverloadResolutionMode.valueOf(it)
-        })
+        }),
+        analysisFlag(AnalysisFlags.explicitApiVersion, if (apiVersionString != null) true else null)
     )
 
     if (apiVersionString == null && languageFeaturesString == null && analysisFlags.isEmpty()) {