Remove the mandatory x86-64 features from its feature list

The x86-64 architecture mandates support for MMX and SSE2, so we don't
need to tell that the compiler generates them. They're implied.

This could serve to determine that the user specified no -march= or -m
flags that affect the architecture on the CMAKE_CXX_FLAGS, but fails if
the compiler does that on its own for this particular target. For
example, both for Android and macOS, the minimum feature set is SSSE3
for 32-bit and SSE4.1 for 64-bit.

Change-Id: I76216ced393445a4ae2dfffd172a94b17e8a9a37
Reviewed-by: Allan Sandfeld Jensen <[email protected]>

config.tests/arch/arch.cpp

@@ -141,7 +141,7 @@ const char msg2[] = "==Qt=magic=Qt== Sub-architecture:"
 // Leading-Zero bit count, Intel Core 4th Generation ("Haswell")
 " lzcnt"
 #endif
-#ifdef __MMX__
+#if defined(__MMX__) && defined(__i386__)
 // Multimedia Extensions, Pentium MMX, AMD K6-2
 " mmx"
 #endif
@@ -198,11 +198,11 @@ const char msg2[] = "==Qt=magic=Qt== Sub-architecture:"
 // Shadow stack, Intel processor TBA
 " shstk"
 #endif
-#if defined(__SSE__) || (defined(_M_IX86_FP) && _M_IX86_FP >= 1) || defined(_M_X64)
+#if (defined(__SSE__) && defined(__i386__)) || (defined(_M_IX86_FP) && _M_IX86_FP >= 1 && defined(_M_IX86))
 // Streaming SIMD Extensions, Intel Pentium III, AMD Athlon
 " sse"
 #endif
-#if defined(__SSE2__) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2) || defined(_M_X64)
+#if (defined(__SSE2__) && defined(__i386__)) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2 && defined(_M_IX86))
 // SSE2, Intel Pentium-M, Intel Pentium 4, AMD Opteron and Athlon 64
 " sse2"
 #endif