disableMarchNative: also disable ADX in BLST (#2175)

config.nims

@@ -40,9 +40,13 @@ if defined(windows):
 # and larger arithmetic use cases, along with register starvation issues. When
 # engineering a more portable binary release, this should be tweaked but still
 # use at least -msse2 or -msse3.
+#
+# Since ADX is only available on new CPUs, we want to disable it for generic
+# binaries (BLST autodetects it with no other way to opt-out than at the C
+# compiler level).
 if defined(disableMarchNative):
-  switch("passC", "-msse3")
-  switch("passL", "-msse3")
+  switch("passC", "-msse3 -mno-adx")
+  switch("passL", "-msse3 -mno-adx")
 else:
   switch("passC", "-march=native")
   switch("passL", "-march=native")