ovmf: Disable lto to aid reproducibility

lto tends to break reproducibility and makes ovmf near impossible to debug
reproducibility issues in. Disable it and supress the warnings that then
generates from Werror.

(From OE-Core rev: 627b6ed763eca90192203932784872b60a65fcaa)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/ovmf/ovmf_git.bb

@@ -102,15 +102,22 @@ fix_toolchain_append_class-native() {
     # to make ovmf-native reusable across distros.
     sed -i \
         -e 's#^\(DEFINE GCC.*DLINK.*FLAGS  *=\)#\1 -fuse-ld=bfd#' \
+        -e 's#-flto#-fno-lto#g' \
+        -e 's#-DUSING_LTO##g' \
         ${S}/BaseTools/Conf/tools_def.template
 }
 
+# We disable lto above since the results are not reproducible and make it hard to compare
+# binary build aretfacts to debug reproducibility problems.
+# Surprisingly, if you disable lto, you see compiler warnings which are fatal. We therefore
+# have to hack warnings overrides into GCC_PREFIX_MAP to allow it to build.
+
 # We want to pass ${DEBUG_PREFIX_MAP} to gcc commands and also pass in
 # --debug-prefix-map to nasm (we carry a patch to nasm for this). The
 # tools definitions are built by ovmf-native so we need to pass this in
 # at target build time when we know the right values.
 export NASM_PREFIX_MAP = "--debug-prefix-map=${WORKDIR}=/usr/src/debug/ovmf/${EXTENDPE}${PV}-${PR}"
-export GCC_PREFIX_MAP = "${DEBUG_PREFIX_MAP}"
+export GCC_PREFIX_MAP = "${DEBUG_PREFIX_MAP} -Wno-stringop-overflow -Wno-maybe-uninitialized"
 
 GCC_VER="$(${CC} -v 2>&1 | tail -n1 | awk '{print $3}')"