qtbase: don't use neon flags on arm64

NEON is mandatory for aarch64 and compiler doesn't recognize
-mfpu=neon commandline argument.

Change-Id: I36e9c40e3fd3604d4895da0526152e90b2165770
Reviewed-by: Qt CMake Build Bot
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtCompilerOptimization.cmake

@@ -62,7 +62,7 @@ if(GCC OR CLANG)
     set(QT_CFLAGS_AVX512VBMI "-mavx512vbmi")
     set(QT_CFLAGS_AESNI      "-maes")
     set(QT_CFLAGS_SHANI      "-msha")
-    if(NOT APPLE_UIKIT)
+    if(NOT APPLE_UIKIT AND NOT QT_64BIT)
         set(QT_CFLAGS_NEON   "-mfpu=neon")
     endif()
     set(QT_CFLAGS_MIPS_DSP   "-mdsp")