Add -D__ANDROID_NATIVE_BRIDGE__ to native_bridge targets

And remove dual meaning from arm_on_x86 target. It was set for x86
targets with arm support and for arm targets with x86 support - and that
2nd one was abused for native_bridge version of RenderScript.

It's much safer and cleaner to rely on __ANDROID_NATIVE_BRIDGE__ there
while leaving arm_on_x86 to mean "x86 binary built in the image with arm
support".

It's only used by bcc compiler which is in canadian-cross situation here:
it's pure x86-64 binary, but it needs to know about ALL supported
architectures on device because it needs to include appropriate codegen
module.

Bug: http://b/153609531

Test: cts-tradefed run cts --abi armeabi-v7a -m CtsRsCppTestCases
Test: cts-tradefed run cts --abi arm64-v8a -m CtsRsCppTestCases

Change-Id: I869212e0b82eeaa30361a4e183d5c862ab40ef12

cc/compiler.go

@@ -345,6 +345,10 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags, deps
 		}
 	}
 
+	if ctx.Target().NativeBridge == android.NativeBridgeEnabled {
+		flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_NATIVE_BRIDGE__")
+	}
+
 	instructionSet := String(compiler.Properties.Instruction_set)
 	if flags.RequiredInstructionSet != "" {
 		instructionSet = flags.RequiredInstructionSet