fix checking the '-march' flag (facebook#5766)

Summary:
Hi! guys,

I got errors on the ARM machine.

before:

```console
$ make static_lib
...
g++: error: unrecognized argument in option '-march=armv8-a+crc+crypto'
g++: note: valid arguments to '-march=' are: armv2 armv2a armv3 armv3m armv4 armv4t armv5 armv5e armv5t armv5te armv6 armv6-m armv6j armv6k armv6kz armv6s-m armv6t2 armv6z armv6zk armv7 armv7-a armv7-m armv7-r armv7e-m armv7ve armv8-a armv8-a+crc armv8.1-a armv8.1-a+crc iwmmxt iwmmxt2 native
```

Thanks!
Pull Request resolved: facebook#5766

Differential Revision: D17191117

fbshipit-source-id: 7a61e3a2a4a06f37faeb8429bd7314da54ec5868

Makefile

@@ -143,7 +143,7 @@ CFLAGS +=  -DHAVE_POWER8
 HAVE_POWER8=1
 endif
 
-ifeq (,$(shell $(CXX) -fsyntax-only -march=armv8-a+crc -xc /dev/null 2>&1))
+ifeq (,$(shell $(CXX) -fsyntax-only -march=armv8-a+crc+crypto -xc /dev/null 2>&1))
 CXXFLAGS += -march=armv8-a+crc+crypto
 CFLAGS += -march=armv8-a+crc+crypto
 ARMCRC_SOURCE=1