ghc_set_gcc_flags: only reduce GCC for s390x for ghc < 9.2

This should really just be for unregisterised ghc

$ ghc --info | grep reg
 ,("Unregisterised","NO")

macros.ghc

@@ -78,11 +78,12 @@ fi\
 %ghc_set_gcc_flags\
 %global _lto_cflags %{nil}\
 %global __brp_strip_lto %{nil}\
-# -Wunused-label is extremely noisy\
+CFLAGS="${CFLAGS:-%optflags}"\
 %ifarch s390x\
+%if %[v"%{ghc_version}" < v"9.2"]\
+# -Wunused-label is extremely noisy\
 CFLAGS="$(echo ${CFLAGS:-%optflags} | sed -e 's/-Wall //' -e 's/-Werror=format-security //')"\
-%else\
+%endif\
-CFLAGS="${CFLAGS:-%optflags}"\
 %endif\
 export CFLAGS\
 %undefine _package_note_flags\