disable precompiled headers, solves problem on MirBSD

toolchain/gcc/Makefile

@@ -20,6 +20,7 @@ GCC_CONFOPTS=		--prefix=$(STAGING_TOOLS) \
 			--disable-multilib \
 			--disable-sjlj-exceptions \
 			--disable-libssp \
+			--disable-libstdcxx-pch \
 			--disable-nls 
 
 ifeq ($(ADK_TARGET_NO_FPU),y)