From: Ruizhi Zhong <ruizhi.zhong88@gmail.com>
Date: Fri, 2 Oct 2026 00:15:00 +0800
Subject: [PATCH] cmake: accept externally supplied CXXFLAGS

Gentoo's cmake.eclass clears CMAKE_CXX_FLAGS_RELEASE and supplies the user's
optimization flags through CMAKE_CXX_FLAGS. Only diagnose an empty flag set
when both variables are empty, preserving the upstream guard for a poisoned
compiler configuration without rejecting Gentoo's deliberate setup.

Upstream-Status: Not submitted (Gentoo-specific flag handling)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,6 +8,7 @@
 # build still succeeds, and inference runs roughly 400x slower because nothing
 # -- including the HIP device code -- is compiled with -O3. Fail loudly instead.
 if (CMAKE_BUILD_TYPE STREQUAL "Release" AND CMAKE_CXX_FLAGS_RELEASE STREQUAL ""
+        AND CMAKE_CXX_FLAGS STREQUAL ""
         AND CMAKE_CXX_COMPILER_ID MATCHES "Clang|GNU")
     message(FATAL_ERROR
         "CMAKE_BUILD_TYPE=Release but CMAKE_CXX_FLAGS_RELEASE is empty, so this "