--- binutils-apple-11.3.1.ebuild.orig        2020-12-03 11:33:23.000000000 -0600
+++ binutils-apple-11.3.1.ebuild     2020-12-03 11:32:56.000000000 -0600
@@ -79,6 +79,10 @@
        mkdir -p include/mach-o || die
        # never present because it's private
        cp ../../${DYLD}/include/mach-o/dyld_priv.h include/mach-o || die
+       # TARGET_OS_BRIDGE is undefined in TargetConditionals.h of newer MacOSX.sdk.
+       # We don't target BridgeOS. Disable it to avoid errors when clang adds:
+       # -Werror,-Wundef-prefix=TARGET_OS_
+       sed -i -e 's/#if TARGET_OS_BRIDGE/#if 0/' include/mach-o/dyld_priv.h
 
        local VER_STR="\"@(#)PROGRAM:ld  PROJECT:${LD64} (Gentoo ${PN}-${PVR})\\n\""
        echo "char ldVersionString[] = ${VER_STR};" > version.cpp