Adds x64 arch-specific test

Summary:
Adds x64 arch-specific test inside the
if HAVE_X86_64
Signed-off-by: Nicholas Ormrod <njormrod@fb.com>

Test Plan: tests

Reviewed By: markisaa@fb.com

Subscribers: folly-diffs@, yfeldblum, chalfant

FB internal diff: D1999428

Tasks: 6783581

Signature: t1:1999428:1429220350:4287342a5a99823c9e4ffe20d0e47039f9fdbc0b

folly/test/Makefile.am

@@ -47,6 +47,10 @@ TESTS += small_vector_test
 discriminated_ptr_test_SOURCES = DiscriminatedPtrTest.cpp
 discriminated_ptr_test_LDADD = libgtestmain.la $(top_builddir)/libfolly.la
 TESTS += discriminated_ptr_test
+
+cpuid_test_SOURCES = CpuIdTest.cpp
+cpuid_test_LDADD = libgtestmain.la $(top_builddir)/libfolly.la
+TESTS += cpuid_test
 endif
 
 sorted_vector_types_test_SOURCES = sorted_vector_test.cpp
@@ -170,10 +174,6 @@ portability_test_SOURCES = PortabilityTest.cpp
 portability_test_LDADD = libgtestmain.la $(top_builddir)/libfolly.la
 TESTS += portability_test
 
-cpuid_test_SOURCES = CpuIdTest.cpp
-cpuid_test_LDADD = libgtestmain.la $(top_builddir)/libfolly.la
-TESTS += cpuid_test
-
 spooky_hash_v1_test_SOURCES = SpookyHashV1Test.cpp
 spooky_hash_v1_test_LDADD = libgtestmain.la $(top_builddir)/libfolly.la $(top_builddir)/libfollybenchmark.la
 TESTS += spooky_hash_v1_test