Mark Huffman Decoder Assembly noexecstack on All Architectures

Apparently, even when the assembly file is empty (because
`ZSTD_ENABLE_ASM_X86_64_BMI2` is false), it still is marked as possibly
needing an executable stack and so the whole library is marked as such. This
commit applies a simple patch for this problem by moving the noexecstack
indication outside the macro guard.

This commit builds on facebook#2857.

This commit addresses facebook#2963.

lib/decompress/huf_decompress_amd64.S

@@ -1,14 +1,14 @@
 #include "../common/portability_macros.h"
 
-#if ZSTD_ENABLE_ASM_X86_64_BMI2
-
 /* Stack marking
  * ref: https://wiki.gentoo.org/wiki/Hardened/GNU_stack_quickstart
  */
 #if defined(__linux__) && defined(__ELF__)
 .section .note.GNU-stack,"",%progbits
 #endif
 
+#if ZSTD_ENABLE_ASM_X86_64_BMI2
+
 /* Calling convention:
  *
  * %rdi contains the first argument: HUF_DecompressAsmArgs*.