removed the XXH_X86DISPATCH_ALLOW_AVX build variable

if the program is compiled with, for example, -mavx2,
then the resulting binary will simply require this instruction set to run.

xxh_x86dispatch.c

@@ -40,9 +40,9 @@
  *
  * Optional add-on.
  *
- * **Compile this file with the default flags for your target.** Do not compile
- * with flags like `-mavx*`, `-march=native`, or `/arch:AVX*`, there will be
- * an error. See @ref XXH_X86DISPATCH_ALLOW_AVX for details.
+ * **Compile this file with the default flags for your target.**
+ * Note that compiling with flags like `-mavx*`, `-march=native`, or `/arch:AVX*`
+ * will make the resulting binary incompatible with cpus not supporting the requested instruction set.
  *
  * @defgroup dispatch x86 Dispatcher
  * @{
@@ -70,34 +70,6 @@ extern "C" {
 #endif
 /*! @endcond */
 
-/*!
- * @def XXH_X86DISPATCH_ALLOW_AVX
- * @brief Disables the AVX sanity check.
- *
- * xxh_x86dispatch.c is intended to be compiled for the minimum target, and
- * it selectively enables SSE2, AVX2, and AVX512 when it is needed.
- *
- * Compiling with options like `-mavx*`, `-march=native`, or `/arch:AVX*`
- * _globally_ will always enable this feature, and therefore makes it
- * undefined behavior to execute on any CPU without said feature.
- *
- * Even if the source code isn't directly using AVX intrinsics in a function,
- * the compiler can still generate AVX code from autovectorization and by
- * "upgrading" SSE2 intrinsics to use the VEX prefixes (a.k.a. AVX128).
- *
- * Define XXH_X86DISPATCH_ALLOW_AVX to ignore this check,
- * thus accepting that the produced binary will not work correctly
- * on any CPU with less features than the ones stated at compilation time.
- */
-#ifdef XXH_DOXYGEN
-#  define XXH_X86DISPATCH_ALLOW_AVX
-#endif
-
-#if defined(__AVX__) && !defined(XXH_X86DISPATCH_ALLOW_AVX)
-#  error "Error: if xxh_x86dispatch.c is compiled with AVX enabled, the resulting binary will crash on sse2-only cpus !! " \
-         "If you nonetheless want to do that, please enable the XXH_X86DISPATCH_ALLOW_AVX build variable"
-#endif
-
 /*!
  * @def XXH_DISPATCH_SCALAR
  * @brief Enables/dispatching the scalar code path.