qsimd.cpp: fix _FORTIFY_SOURCE=2 builds

That option makes printf() and some other functions become always_inline
functions with extent checking. Unfortunately, that also means GCC fails
to inline them when we're not compiling for the same target as
X86_BASELINE.

Fixes: QTBUG-101198
Change-Id: Ibf4acec0f166495998f7fffd16d682c7a7be94d8
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/corelib/CMakeLists.txt

@@ -287,6 +287,7 @@ _qt_internal_setup_deploy_support()
 
 set(corelib_no_pch_sources
     compat/removed_api.cpp
+    global/qsimd.cpp
 )
 
 foreach(src ${corelib_no_pch_sources})

src/corelib/global/qsimd.cpp

@@ -40,6 +40,7 @@
 
 // we need ICC to define the prototype for _rdseed64_step
 #define __INTEL_COMPILER_USE_INTRINSIC_PROTOTYPES
+#undef _FORTIFY_SOURCE      // otherwise, the always_inline from stdio.h fail to inline
 
 #include "qsimd_p.h"
 #include "qalgorithms.h"