Build: remove obsolete compiler arguments

These compiler arguments enable features which are enabled by default in
the current Kotlin anyway.

The only exception is in :compiler:cli which uses an old language
version.

kotlin-native/backend.native/build.gradle

@@ -185,12 +185,11 @@ targetList.each { target ->
         args = [*konanArgs,
                 '-output', project(':kotlin-native:runtime').file("build/${target}Stdlib"),
                 '-produce', 'library', '-module-name', 'stdlib',
-                '-Xmulti-platform', '-Xopt-in=kotlin.RequiresOptIn', '-Xinline-classes',
+                '-Xmulti-platform', '-Xopt-in=kotlin.RequiresOptIn',
                 '-Xopt-in=kotlin.contracts.ExperimentalContracts',
                 '-Xopt-in=kotlin.ExperimentalMultiplatform',
                 '-Xopt-in=kotlin.native.internal.InternalForKotlinNative',
                 '-Xopt-in=kotlin.native.SymbolNameIsDeprecated',
-                '-Xallow-result-return-type',
                 *commonSrc.toList(),
                 *testAnnotationCommon.toList(),
                 *testCommon.toList(),