Fix sysroot for standalone GYP build on ARM. 
Fix sysroot for standalone GYP build on ARM. 

When compiling C files with deps on external libraries, seeing error like this:

CC(target) out/Debug/obj.target/platform/native_client/src/shared/platform/nacl_global_secure_random.o
In file included from ./native_client/src/shared/platform/nacl_secure_random.h:22,
                 from ./native_client/src/shared/platform/nacl_global_secure_random.h:14,
                 from native_client/src/shared/platform/nacl_global_secure_random.c:11:
./native_client/src/shared/platform/linux/nacl_secure_random_types.h:32:26: error: openssl/aes.h: No such file or directory
Review URL: https://chromiumcodereview.appspot.com/9875016

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@8131 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client