Move `FP_ARM_OUTLINE_ATOMICS` to RTS configure

It is just `AC_DEFINE` it belongs there instead.

configure.ac

@@ -1027,10 +1027,6 @@ AC_SUBST([UseLibpthread])
 GHC_ADJUSTORS_METHOD([Target])
 AC_SUBST([UseLibffiForAdjustors])
 
-dnl ** ARM outline atomics
-dnl --------------------------------------------------------------
-FP_ARM_OUTLINE_ATOMICS
-
 dnl ** IPE data compression
 dnl --------------------------------------------------------------
 FP_FIND_LIBZSTD

rts/configure.ac

@@ -129,6 +129,10 @@ case ${HostOS} in
 AC_DEFINE_UNQUOTED([RTS_LINKER_USE_MMAP], [$RtsLinkerUseMmap],
                    [Use mmap in the runtime linker])
 
+dnl ** ARM outline atomics
+dnl --------------------------------------------------------------
+FP_ARM_OUTLINE_ATOMICS
+
 dnl ** IPE data compression
 dnl --------------------------------------------------------------
 AC_DEFINE_UNQUOTED([HAVE_LIBZSTD], [$CABAL_FLAG_libzstd], [Define to 1 if you