Darwin: Use the same `ar` as Soong

Soong uses the copy of `ar` in the OSX SDK instead of the wrapper in
/usr/bin/ar. /usr/bin/ar appears to be a thin wrapper that looks up the
current SDK and passes execution to it. Soong does this so that it can
actually set up a dependency on the tool.

Change-Id: Ia4e4fbe3287539933fa98a1354c3ccee91f4d552
diff --git a/core/combo/HOST_darwin-x86.mk b/core/combo/HOST_darwin-x86.mk
index 076815b..ea384b4 100644
--- a/core/combo/HOST_darwin-x86.mk
+++ b/core/combo/HOST_darwin-x86.mk
@@ -44,7 +44,7 @@
 # HOST_TOOLCHAIN_ROOT is a Darwin-specific define
 $(combo_2nd_arch_prefix)HOST_TOOLCHAIN_FOR_CLANG := $($(combo_2nd_arch_prefix)HOST_TOOLCHAIN_ROOT)
 
-$(combo_2nd_arch_prefix)HOST_AR := $(AR)
+$(combo_2nd_arch_prefix)HOST_AR := $(mac_sdk_path)/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar
 
 $(combo_2nd_arch_prefix)HOST_GLOBAL_CFLAGS += -isysroot $(mac_sdk_root) -mmacosx-version-min=$(mac_sdk_version) -DMACOSX_DEPLOYMENT_TARGET=$(mac_sdk_version)
 $(combo_2nd_arch_prefix)HOST_GLOBAL_LDFLAGS += -isysroot $(mac_sdk_root) -Wl,-syslibroot,$(mac_sdk_root) -mmacosx-version-min=$(mac_sdk_version)
diff --git a/core/combo/HOST_darwin-x86_64.mk b/core/combo/HOST_darwin-x86_64.mk
index a8541ee..eee2ee5 100644
--- a/core/combo/HOST_darwin-x86_64.mk
+++ b/core/combo/HOST_darwin-x86_64.mk
@@ -44,7 +44,7 @@
 # HOST_TOOLCHAIN_ROOT is a Darwin-specific define
 HOST_TOOLCHAIN_FOR_CLANG := $(HOST_TOOLCHAIN_ROOT)
 
-HOST_AR := $(AR)
+HOST_AR := $(mac_sdk_path)/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar
 
 HOST_GLOBAL_CFLAGS += -isysroot $(mac_sdk_root) -mmacosx-version-min=$(mac_sdk_version) -DMACOSX_DEPLOYMENT_TARGET=$(mac_sdk_version)
 HOST_GLOBAL_LDFLAGS += -isysroot $(mac_sdk_root) -Wl,-syslibroot,$(mac_sdk_root) -mmacosx-version-min=$(mac_sdk_version)