Expose the minimum supported SDK version to make.

Right now this is hard coded in two places (here and in
core/binary.mk). Keep it in one place so it's easier to change.

Test: make checkbuild
Bug: None
Change-Id: I2a2c784d4c667b326f871e6144db92753c16c85f

4 files changed, 22 insertions, 7 deletions

diff --git a/android/config.go b/android/config.go
index ee2f40fd..330669dc 100644
--- a/android/config.go
+++ b/android/config.go
@@ -378,6 +378,10 @@ func (c *config) PlatformSdkVersion() string {
 	return strconv.Itoa(c.PlatformSdkVersionInt())
 }
 
+func (c *config) MinSupportedSdkVersion() int {
+	return 9
+}
+
 // Codenames that are active in the current lunch target.
 func (c *config) PlatformVersionActiveCodenames() []string {
 	return c.ProductVariables.Platform_version_active_codenames
diff --git a/android/makevars.go b/android/makevars.go
index 482fbdea..024e0152 100644
--- a/android/makevars.go
+++ b/android/makevars.go
@@ -19,11 +19,20 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"strconv"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 )
 
+func init() {
+	RegisterMakeVarsProvider(pctx, androidMakeVarsProvider)
+}
+
+func androidMakeVarsProvider(ctx MakeVarsContext) {
+	ctx.Strict("MIN_SUPPORTED_SDK_VERSION", strconv.Itoa(ctx.Config().MinSupportedSdkVersion()))
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Interface for other packages to use to declare make variables
 type MakeVarsContext interface {
diff --git a/cc/cc.go b/cc/cc.go
index ba06be24..cfe748b7 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -638,7 +638,7 @@ func (c *Module) begin(ctx BaseModuleContext) {
 		feature.begin(ctx)
 	}
 	if ctx.sdk() {
-		version, err := normalizeNdkApiLevel(ctx.sdkVersion(), ctx.Arch())
+		version, err := normalizeNdkApiLevel(ctx, ctx.sdkVersion(), ctx.Arch())
 		if err != nil {
 			ctx.PropertyErrorf("sdk_version", err.Error())
 		}
diff --git a/cc/ndk_library.go b/cc/ndk_library.go
index 8fbffcf0..fc7cd918 100644
--- a/cc/ndk_library.go
+++ b/cc/ndk_library.go
@@ -110,18 +110,20 @@ func intMax(a int, b int) int {
 	}
 }
 
-func normalizeNdkApiLevel(apiLevel string, arch android.Arch) (string, error) {
+func normalizeNdkApiLevel(ctx android.BaseContext, apiLevel string,
+	arch android.Arch) (string, error) {
+
 	if apiLevel == "current" {
 		return apiLevel, nil
 	}
 
-	minVersion := 9 // Minimum version supported by the NDK.
+	minVersion := ctx.AConfig().MinSupportedSdkVersion()
 	firstArchVersions := map[android.ArchType]int{
-		android.Arm:    9,
+		android.Arm:    minVersion,
 		android.Arm64:  21,
-		android.Mips:   9,
+		android.Mips:   minVersion,
 		android.Mips64: 21,
-		android.X86:    9,
+		android.X86:    minVersion,
 		android.X86_64: 21,
 	}
 
@@ -188,7 +190,7 @@ func shouldUseVersionScript(stub *stubDecorator) (bool, error) {
 func generateStubApiVariants(mctx android.BottomUpMutatorContext, c *stubDecorator) {
 	platformVersion := mctx.AConfig().PlatformSdkVersionInt()
 
-	firstSupportedVersion, err := normalizeNdkApiLevel(c.properties.First_version,
+	firstSupportedVersion, err := normalizeNdkApiLevel(mctx, c.properties.First_version,
 		mctx.Arch())
 	if err != nil {
 		mctx.PropertyErrorf("first_version", err.Error())