Apply optimization workaround to ix86 only

These workarounds where introduced for ix86 in the first place.

In newer versions, they are causing build issues:
https://bugzilla.redhat.com/show_bug.cgi?id=2440395

Enable them conditionally.

Backported from Fedora rawhide commit 5beacdd82355.

vulkan-validation-layers.spec

@@ -35,8 +35,10 @@ Vulkan validation layers
 
 %build
 # Decrease debuginfo verbosity to reduce memory consumption even more
+%ifarch %{ix86}
 %global optflags %(echo %{optflags} | sed 's/-g /-g1 /')
 %global optflags %(echo %{optflags} | sed 's/-O2 /-O1 /')
+%endif
 
 %cmake -DCMAKE_BUILD_TYPE=Release \
        -DBUILD_WERROR=OFF \