Remove support for Darwin 10.6 SDK

Our minimum version is 10.8

Change-Id: I2f1984c2227861a3c784f2a5070853c2d1b250d6
diff --git a/core/combo/HOST_darwin-x86.mk b/core/combo/HOST_darwin-x86.mk
index fc56e52..c1c3caa 100644
--- a/core/combo/HOST_darwin-x86.mk
+++ b/core/combo/HOST_darwin-x86.mk
@@ -32,7 +32,7 @@
 include $(BUILD_COMBOS)/mac_version.mk
 
 $(combo_2nd_arch_prefix)HOST_TOOLCHAIN_ROOT := prebuilts/gcc/darwin-x86/host/i686-apple-darwin-4.2.1
-$(combo_2nd_arch_prefix)HOST_TOOLCHAIN_PREFIX := $($(combo_2nd_arch_prefix)HOST_TOOLCHAIN_ROOT)/bin/i686-apple-darwin$(gcc_darwin_version)
+$(combo_2nd_arch_prefix)HOST_TOOLCHAIN_PREFIX := $($(combo_2nd_arch_prefix)HOST_TOOLCHAIN_ROOT)/bin/i686-apple-darwin11
 $(combo_2nd_arch_prefix)HOST_CC  := $($(combo_2nd_arch_prefix)HOST_TOOLCHAIN_PREFIX)-gcc
 $(combo_2nd_arch_prefix)HOST_CXX := $($(combo_2nd_arch_prefix)HOST_TOOLCHAIN_PREFIX)-g++
 
diff --git a/core/combo/HOST_darwin-x86_64.mk b/core/combo/HOST_darwin-x86_64.mk
index 251455f..ce9d1bb 100644
--- a/core/combo/HOST_darwin-x86_64.mk
+++ b/core/combo/HOST_darwin-x86_64.mk
@@ -32,7 +32,7 @@
 include $(BUILD_COMBOS)/mac_version.mk
 
 HOST_TOOLCHAIN_ROOT := prebuilts/gcc/darwin-x86/host/i686-apple-darwin-4.2.1
-HOST_TOOLCHAIN_PREFIX := $(HOST_TOOLCHAIN_ROOT)/bin/i686-apple-darwin$(gcc_darwin_version)
+HOST_TOOLCHAIN_PREFIX := $(HOST_TOOLCHAIN_ROOT)/bin/i686-apple-darwin11
 HOST_CC  := $(HOST_TOOLCHAIN_PREFIX)-gcc
 HOST_CXX := $(HOST_TOOLCHAIN_PREFIX)-g++
 
diff --git a/core/combo/mac_version.mk b/core/combo/mac_version.mk
index f6bd852..92006aa 100644
--- a/core/combo/mac_version.mk
+++ b/core/combo/mac_version.mk
@@ -41,10 +41,4 @@
 $(error Stop.)
 endif
 
-ifeq ($(mac_sdk_version),10.6)
-  gcc_darwin_version := 10
-else
-  gcc_darwin_version := 11
-endif
-
 endif  # ifndef build_mac_version