Add __ANDROID_SDK_VERSION__=<ver> macro

sdk_version is passed for relevant variants.
If not specified or "current",
it maps to "10000" for platform variants, and
"min_sdk_version" of the apex for apex variants.

Bug: 150860940
Test: m (soong test)
      manually check build.ninja
Change-Id: I5102ab0c5086b5ad29d16ac45af55d32062167b4
diff --git a/apex/apex_test.go b/apex/apex_test.go
index 2b13197..a2dcfaf 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -1687,6 +1687,7 @@
 			name: "otherapex",
 			key: "myapex.key",
 			native_shared_libs: ["mylib", "mylib2"],
+			min_sdk_version: "29",
 		}
 
 		apex_key {
@@ -1721,15 +1722,18 @@
 	// non-APEX variant does not have __ANDROID_APEX__ defined
 	mylibCFlags := ctx.ModuleForTests("mylib", "android_arm64_armv8-a_static").Rule("cc").Args["cFlags"]
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX__")
+	ensureContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__=10000")
 
-	// APEX variant has __ANDROID_APEX__ defined
+	// APEX variant has __ANDROID_APEX__ and __ANDROID_APEX_SDK__ defined
 	mylibCFlags = ctx.ModuleForTests("mylib", "android_arm64_armv8-a_static_myapex").Rule("cc").Args["cFlags"]
 	ensureContains(t, mylibCFlags, "-D__ANDROID_APEX__")
+	ensureContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__=10000")
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_MYAPEX__")
 
-	// APEX variant has __ANDROID_APEX__ defined
+	// APEX variant has __ANDROID_APEX__ and __ANDROID_APEX_SDK__ defined
 	mylibCFlags = ctx.ModuleForTests("mylib", "android_arm64_armv8-a_static_otherapex").Rule("cc").Args["cFlags"]
 	ensureContains(t, mylibCFlags, "-D__ANDROID_APEX__")
+	ensureContains(t, mylibCFlags, "-D__ANDROID_SDK_VERSION__=29")
 	ensureNotContains(t, mylibCFlags, "-D__ANDROID_APEX_OTHERAPEX__")
 
 	// When cc_library sets use_apex_name_macro: true