Remove obsolete conditional

Now in unbundled or PDK build we use prebuilt aidl in place.
We don't need the conditional any more.
Also this expose aidl-cpp to pseudo unbundled build in the platform
source tree.

Bug: 27488208
Change-Id: I2c16700e764e2de410ea579b975e11a0d56429c2
(cherry-pick from commit 6215b9569ff2056b78893ce9a5007d419ef203f5)
diff --git a/Android.mk b/Android.mk
index 97d9e35..5b844e4 100644
--- a/Android.mk
+++ b/Android.mk
@@ -24,9 +24,6 @@
   aidl_module_host_os := darwin linux
 endif
 
-# This tool is prebuilt if we're doing an app-only build.
-ifeq ($(TARGET_BUILD_APPS),)
-
 # Logic shared between aidl and its unittests
 include $(CLEAR_VARS)
 LOCAL_MODULE := libaidl-common
@@ -121,8 +118,6 @@
 LOCAL_LDLIBS_linux := -lrt
 include $(BUILD_HOST_NATIVE_TEST)
 
-endif # No TARGET_BUILD_APPS or TARGET_BUILD_PDK
-
 #
 # Everything below here is used for integration testing of generated AIDL code.
 #