accel/tcg: Remove special case for GCC < 4.6

Since commit efc6c070 ("configure: Add a test for the
minimum compiler version") the minimum compiler version
required for GCC is 4.8.

We can safely remove the special case for GCC 4.6 introduced
in commit 0448f5f8 ("cpu-exec: Fix compiler warning
(-Werror=clobbered)").
No change for Clang as we don't know.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20201210134752.780923-3-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/tcg/cpu-exec.c

@@ -724,7 +724,7 @@ int cpu_exec(CPUState *cpu)
 
     /* prepare setjmp context for exception handling */
     if (sigsetjmp(cpu->jmp_env, 0) != 0) {
-#if defined(__clang__) || !QEMU_GNUC_PREREQ(4, 6)
+#if defined(__clang__)
         /* Some compilers wrongly smash all local variables after
          * siglongjmp. There were bug reports for gcc 4.5.0 and clang.
          * Reload essential local variables here for those compilers.