fix: disable LSX for loong64

-mlsx is enabled globally but is not yet available in LLVM 17. Loongson will submit a backport later and we can enable this then.

Author: MingcongBai

debian/rules

@@ -74,6 +74,13 @@ else
   export DEB_CFLAGS_MAINT_STRIP = -g -O2
   export DEB_CXXFLAGS_MAINT_STRIP = -g -O2
 endif
+
+ifeq ($(DEB_BUILD_ARCH),loong64)
+	# FIXME: -mlsx is not yet available for Clang.
+	export DEB_CFLAGS_MAINT_STRIP = -mlsx
+	export DEB_CXXFLAGS_MAINT_STRIP = -mlsx
+endif
+
 include /usr/share/dpkg/buildflags.mk
 
 # We use a stage2 build. It means that a first clang is built using gcc,