Disable ABI dumps on Darwin.

I'm not sure why these targets are getting built as part of the sdk
build anyway, but we don't need them.

Test: treehugger
Bug: http://b/156513478
Bug: http://b/190394921
Change-Id: I1ea0e75f459ad7cad648f96b67a4f2424d36fda7

cc/ndk_abi.go

@@ -46,7 +46,7 @@ func (n *ndkAbiDumpSingleton) GenerateBuildActions(ctx android.SingletonContext)
 
 		if m, ok := module.(*Module); ok {
 			if installer, ok := m.installer.(*stubDecorator); ok {
-				if canDumpAbi(m) {
+				if canDumpAbi() {
 					depPaths = append(depPaths, installer.abiDumpPath)
 				}
 			}

cc/ndk_library.go

@@ -17,6 +17,7 @@ package cc
 import (
 	"fmt"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"sync"
 
@@ -332,12 +333,12 @@ func (this *stubDecorator) findPrebuiltAbiDump(ctx ModuleContext,
 }
 
 // Feature flag.
-func canDumpAbi(module android.Module) bool {
-	return true
+func canDumpAbi() bool {
+	return runtime.GOOS != "darwin"
 }
 
 // Feature flag to disable diffing against prebuilts.
-func canDiffAbi(module android.Module) bool {
+func canDiffAbi() bool {
 	return false
 }
 
@@ -452,9 +453,9 @@ func (c *stubDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) O
 	nativeAbiResult := parseNativeAbiDefinition(ctx, symbolFile, c.apiLevel, "")
 	objs := compileStubLibrary(ctx, flags, nativeAbiResult.stubSrc)
 	c.versionScriptPath = nativeAbiResult.versionScript
-	if canDumpAbi(ctx.Module()) {
+	if canDumpAbi() {
 		c.dumpAbi(ctx, nativeAbiResult.symbolList)
-		if canDiffAbi(ctx.Module()) {
+		if canDiffAbi() {
 			c.diffAbi(ctx)
 		}
 	}