suppress -Wmaybe-uninitialized in #12019

[ghstack-poisoned]

Author: swolchok

test/build_size_test.sh

@@ -15,7 +15,10 @@ EXTRA_BUILD_ARGS="${@:-}"
 # TODO(#8357): Remove -Wno-int-in-bool-context
 # TODO: Replace -ET_HAVE_PREAD=0 with a CMake option.
 #  FileDataLoader used in the size_test breaks baremetal builds with pread when missing.
-COMMON_CXXFLAGS="-fno-exceptions -fno-rtti -Wall -Werror -Wno-int-in-bool-context -DET_HAVE_PREAD=0"
+# -Werror=maybe-uninitialized causes failures with GCC 9.5, which we
+# -currently use in CI. There were known issues with this warning and
+# -std::optional: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635
+COMMON_CXXFLAGS="-fno-exceptions -fno-rtti -Wall -Werror -Wno-int-in-bool-context -Wno-maybe-uninitialized -DET_HAVE_PREAD=0"
 
 cmake_install_executorch_lib() {
   echo "Installing libexecutorch.a"