Merge changes from topic "update-prebuilts-r18b"

* changes:
  Don't use libandroid_support post-21.
  Up the NDK's minimum supported API level.
  Remove legacy NDK code.

android/config.go

@@ -482,7 +482,7 @@ func (c *config) PlatformSdkCodename() string {
 }
 
 func (c *config) MinSupportedSdkVersion() int {
-	return 14
+	return 16
 }
 
 func (c *config) DefaultAppTargetSdkInt() int {

cc/compiler.go

@@ -299,6 +299,7 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags, deps
 	}
 
 	if ctx.useSdk() {
+		// TODO: Switch to --sysroot.
 		// The NDK headers are installed to a common sysroot. While a more
 		// typical Soong approach would be to only make the headers for the
 		// library you're using available, we're trying to emulate the NDK
@@ -307,6 +308,7 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags, deps
 			"-isystem "+getCurrentIncludePath(ctx).String(),
 			"-isystem "+getCurrentIncludePath(ctx).Join(ctx, config.NDKTriple(tc)).String())
 
+		// TODO: Migrate to API suffixed triple?
 		// Traditionally this has come from android/api-level.h, but with the
 		// libc headers unified it must be set by the build system since we
 		// don't have per-API level copies of that header now.
@@ -316,14 +318,6 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags, deps
 		}
 		flags.GlobalFlags = append(flags.GlobalFlags,
 			"-D__ANDROID_API__="+version)
-
-		// Until the full NDK has been migrated to using ndk_headers, we still
-		// need to add the legacy sysroot includes to get the full set of
-		// headers.
-		legacyIncludes := fmt.Sprintf(
-			"prebuilts/ndk/current/platforms/android-%s/arch-%s/usr/include",
-			ctx.sdkVersion(), ctx.Arch().ArchType.String())
-		flags.SystemIncludeFlags = append(flags.SystemIncludeFlags, "-isystem "+legacyIncludes)
 	}
 
 	if ctx.useVndk() {

cc/stl.go

@@ -17,6 +17,7 @@ package cc
 import (
 	"android/soong/android"
 	"fmt"
+	"strconv"
 )
 
 func getNdkStlFamily(m *Module) string {
@@ -110,6 +111,26 @@ func (stl *stl) begin(ctx BaseModuleContext) {
 	}()
 }
 
+func needsLibAndroidSupport(ctx BaseModuleContext) bool {
+	versionStr, err := normalizeNdkApiLevel(ctx, ctx.sdkVersion(), ctx.Arch())
+	if err != nil {
+		ctx.PropertyErrorf("sdk_version", err.Error())
+	}
+
+	if versionStr == "current" {
+		return false
+	}
+
+	version, err := strconv.Atoi(versionStr)
+	if err != nil {
+		panic(fmt.Sprintf(
+			"invalid API level returned from normalizeNdkApiLevel: %q",
+			versionStr))
+	}
+
+	return version < 21
+}
+
 func (stl *stl) deps(ctx BaseModuleContext, deps Deps) Deps {
 	switch stl.Properties.SelectedStl {
 	case "libstdc++":
@@ -141,7 +162,9 @@ func (stl *stl) deps(ctx BaseModuleContext, deps Deps) Deps {
 		} else {
 			deps.StaticLibs = append(deps.StaticLibs, stl.Properties.SelectedStl, "ndk_libc++abi")
 		}
+		if needsLibAndroidSupport(ctx) {
 			deps.StaticLibs = append(deps.StaticLibs, "ndk_libandroid_support")
+		}
 		if ctx.Arch().ArchType == android.Arm {
 			deps.StaticLibs = append(deps.StaticLibs, "ndk_libunwind")
 		}