Reduce rustc's own optimization on i686

.rust.metadata

@@ -0,0 +1,2 @@
+9ad7bb54dc9572c103b855cdcc823addbb34d15d rustc-1.75.0-src.tar.xz
+55eaa32c99cc8ec970f2db2d340a605724589f9b wasi-libc-bd950eb128bff337153de217b11270f948d04bb4.tar.gz

rust.spec

@@ -656,11 +656,13 @@ end}
 %{export_rust_env}
 
 %ifarch %{arm} %{ix86}
-# full debuginfo is exhausting memory; just do libstd for now
+# full debuginfo and compiler opts are exhausting memory; just do libstd for now
 # https://github.com/rust-lang/rust/issues/45854
 %define enable_debuginfo --debuginfo-level=0 --debuginfo-level-std=2
+%define enable_rust_opts --set rust.codegen-units-std=1
 %else
 %define enable_debuginfo --debuginfo-level=2
+%define enable_rust_opts --set rust.codegen-units=1 --set rust.lto=thin
 %endif
 
 # Some builders have relatively little memory for their CPU count.
@@ -727,8 +729,7 @@ test -r "%{profiler}"
   --disable-llvm-static-stdcpp \
   --disable-rpath \
   %{enable_debuginfo} \
-  --set rust.codegen-units=1 \
-  --set rust.lto=thin \
+  %{enable_rust_opts} \
   --set build.build-stage=2 \
   --set build.doc-stage=2 \
   --set build.install-stage=2 \