cross-powerpc64-linux-musl: patch out __gnu_linux__

See the matching change in gcc.

[ci skip]

srcpkgs/cross-powerpc64-linux-musl/template

@@ -9,7 +9,7 @@ _sysroot="/usr/${_triplet}"
 
 pkgname=cross-${_triplet}
 version=0.30
-revision=3
+revision=4
 short_desc="Cross toolchain for powerpc64 with musl"
 maintainer="q66 <daniel@octaforge.org>"
 homepage="https://www.voidlinux.org/"
@@ -89,6 +89,9 @@ _gcc_bootstrap() {
 
 	sed -i 's/lib64/lib/' gcc/config/rs6000/linux64.h
 
+	# REMOVE WITH 9.1
+	sed -i 's/ \-D__gnu_linux__//' gcc/config/rs6000/sysv4.h
+
 	msg_normal "Building cross gcc bootstrap\n"
 
 	[ ! -d ../gcc-bootstrap ] && mkdir ../gcc-bootstrap