chroot-grep: fix musl bootstrap under some conditions

srcpkgs/chroot-grep/template

@@ -15,6 +15,11 @@ checksum=b960541c499619efd6afe1fa795402e4733c8e11ebf9fafccc0bb4bccdc5b514
 conflicts="grep>=0"
 provides="grep-${version}_${revision}"
 
+if [ "$XBPS_TARGET_LIBC" = musl ]; then
+	export ac_cv_lib_error_at_line=no
+	export ac_cv_header_sys_cdefs_h=no
+fi
+
 post_install() {
 	rm -rf ${DESTDIR}/usr/share/info ${DESTDIR}/usr/share/man
 }