Decouple platform compiler and NDK library versioning.

TARGET_GCC_VERSION: select compiler from prebuilts/gcc/...
TARGET_NDK_GCC_VERSION: select libraries from prebuilts/ndk/...

Change-Id: I4422a42cdc97aa92b40798014cba82c3c123bbd2
diff --git a/core/combo/TARGET_linux-arm.mk b/core/combo/TARGET_linux-arm.mk
index 5cb99b4..f698ef5 100644
--- a/core/combo/TARGET_linux-arm.mk
+++ b/core/combo/TARGET_linux-arm.mk
@@ -34,6 +34,9 @@
 TARGET_$(combo_2nd_arch_prefix)ARCH_VARIANT := armv5te
 endif
 
+# Decouple NDK library selection with platform compiler version
+$(combo_2nd_arch_prefix)TARGET_NDK_GCC_VERSION := 4.8
+
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
 $(combo_2nd_arch_prefix)TARGET_GCC_VERSION := 4.8
 else
diff --git a/core/combo/TARGET_linux-arm64.mk b/core/combo/TARGET_linux-arm64.mk
index 08603b8..e894f6d 100644
--- a/core/combo/TARGET_linux-arm64.mk
+++ b/core/combo/TARGET_linux-arm64.mk
@@ -34,6 +34,9 @@
 TARGET_ARCH_VARIANT := armv8
 endif
 
+# Decouple NDK library selection with platform compiler version
+TARGET_NDK_GCC_VERSION := 4.8
+
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
 TARGET_GCC_VERSION := 4.8
 else
diff --git a/core/combo/TARGET_linux-mips.mk b/core/combo/TARGET_linux-mips.mk
index 68300e1..27304ee 100644
--- a/core/combo/TARGET_linux-mips.mk
+++ b/core/combo/TARGET_linux-mips.mk
@@ -34,6 +34,9 @@
 TARGET_$(combo_2nd_arch_prefix)ARCH_VARIANT := mips32r2-fp
 endif
 
+# Decouple NDK library selection with platform compiler version
+$(combo_2nd_arch_prefix)TARGET_NDK_GCC_VERSION := 4.8
+
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
 $(combo_2nd_arch_prefix)TARGET_GCC_VERSION := 4.8
 else
diff --git a/core/combo/TARGET_linux-mips64.mk b/core/combo/TARGET_linux-mips64.mk
index 118582b..36b70ad 100644
--- a/core/combo/TARGET_linux-mips64.mk
+++ b/core/combo/TARGET_linux-mips64.mk
@@ -34,6 +34,9 @@
 TARGET_ARCH_VARIANT := mips64r2
 endif
 
+# Decouple NDK library selection with platform compiler version
+TARGET_NDK_GCC_VERSION := 4.8
+
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
 TARGET_GCC_VERSION := 4.8
 else
diff --git a/core/combo/TARGET_linux-x86.mk b/core/combo/TARGET_linux-x86.mk
index 80df1a4..1361be2 100644
--- a/core/combo/TARGET_linux-x86.mk
+++ b/core/combo/TARGET_linux-x86.mk
@@ -22,6 +22,9 @@
 TARGET_$(combo_2nd_arch_prefix)ARCH_VARIANT := x86
 endif
 
+# Decouple NDK library selection with platform compiler version
+$(combo_2nd_arch_prefix)TARGET_NDK_GCC_VERSION := 4.8
+
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
 $(combo_2nd_arch_prefix)TARGET_GCC_VERSION := 4.8
 else
diff --git a/core/combo/TARGET_linux-x86_64.mk b/core/combo/TARGET_linux-x86_64.mk
index fb9bacf..2e06263 100644
--- a/core/combo/TARGET_linux-x86_64.mk
+++ b/core/combo/TARGET_linux-x86_64.mk
@@ -22,6 +22,9 @@
 TARGET_ARCH_VARIANT := x86_64
 endif
 
+# Decouple NDK library selection with platform compiler version
+TARGET_NDK_GCC_VERSION := 4.8
+
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
 TARGET_GCC_VERSION := 4.8
 else