Fix mac SDK builds.

libBionicTests isn't built for Mac hosts, so we can't
build bionic cts tests either. Even though CTS tests run
on the target (not the host) bionic-unit-tests-cts_list
can't be built, and is used to generate the test
description XML.

Note: This shows up as a build breakage on
mirror-aosp-master but not master because the build bot
doesn't use checkbuild on that target.

Change-Id: I23b980160945f071264cfbb085a796416d78afb5
diff --git a/CtsTestCaseList.mk b/CtsTestCaseList.mk
index dab7b67..8a37b72 100644
--- a/CtsTestCaseList.mk
+++ b/CtsTestCaseList.mk
@@ -139,7 +139,10 @@
 cts_native_exes := \
 	NativeMediaTest_SL \
 	NativeMediaTest_XA \
-	bionic-unit-tests-cts \
+
+ifeq ($(HOST_OS)-$(HOST_ARCH),$(filter $(HOST_OS)-$(HOST_ARCH),linux-x86 linux-x86_64))
+cts_native_exes += bionic-unit-tests-cts
+endif
 
 cts_ui_tests := \
     CtsUiAutomatorTests
@@ -164,4 +167,4 @@
 
 
 # The following files will be placed in the tools directory of the CTS distribution
-CTS_TOOLS_LIST :=
\ No newline at end of file
+CTS_TOOLS_LIST :=