Properly factor Native Client defines to support NaCl OS on ARM and x86

test/CodeGen/arm-aapcs-vfp.c

 // REQUIRES: arm-registered-target
 // RUN: %clang_cc1 -triple thumbv7-apple-darwin9 \
 // RUN:   -target-abi aapcs \
 // RUN:   -target-cpu cortex-a8 \
 // RUN:   -mfloat-abi hard \
 // RUN:   -ffreestanding \
 // RUN:   -emit-llvm -w -o - %s | FileCheck %s
 
+// RUN: %clang_cc1 -triple armv7-unknown-nacl-gnueabi \
+// RUN:  -target-cpu cortex-a8 \
+// RUN:  -mfloat-abi hard \
+// RUN:  -ffreestanding \
+// RUN:  -emit-llvm -w -o - %s | FileCheck %s
+
 #include <arm_neon.h>
 
 struct homogeneous_struct {
   float f[2];
   float f3;
   float f4;
 };
 // CHECK: define arm_aapcs_vfpcc %struct.homogeneous_struct @test_struct(float %{{.*}}, float %{{.*}}, float %{{.*}}, float %{{.*}})
 extern struct homogeneous_struct struct_callee(struct homogeneous_struct);
 struct homogeneous_struct test_struct(struct homogeneous_struct arg) {
@@ skipping 66 matching lines @@
 };
 // CHECK: define arm_aapcs_vfpcc void @test_neon(<8 x i8> %{{.*}}, <8 x i8> %{{.*}}, <2 x i32> %{{.*}}, <4 x i16> %{{.*}})
 extern void neon_callee(struct neon_struct);
 void test_neon(struct neon_struct arg) {
   neon_callee(arg);
 }
 
 // CHECK: define arm_aapcs_vfpcc void @f33(%struct.s33* byval %s)
 struct s33 { char buf[32*32]; };
 void f33(struct s33 s) { }