Add byacc parser generator

This is meant to replace heirloom yacc for compiling pre-musl parsers.
Unlike heirloom yacc, it's in the public domain, and can be linked with
meslibc without licensing concerns.

steps/byacc-20240109/pass1.kaem

@@ -0,0 +1,51 @@
+#!/bin/sh
+
+# SPDX-FileCopyrightText: 2021 Andrius Štikonas <andrius@stikonas.eu>
+# SPDX-FileCopyrightText: 2021-22 fosslinux <fosslinux@aussies.space>
+# SPDX-FileCopyrightText: 2024 Gábor Stefanik <netrolller.3d@gmail.com>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+set -ex
+
+# Check tarball checksums
+checksum-transcriber sources
+sha256sum -c sources.SHA256SUM
+
+mkdir build src
+cd build
+
+# Extract
+cp ${DISTFILES}/${pkg}.tgz ../src/${pkg}.tar.gz
+gunzip -f ../src/${pkg}.tar.gz
+tar xf ../src/${pkg}.tar
+rm -r ../src/
+cd ${pkg}
+
+# Prepare
+cp ../../files/Makefile .
+
+# meslibc has no fgetpos/fsetpos - emulate using fseek/ftell
+sed -i -e "s/fpos_t/long/" -e "s/fgetpos(f, &save_area.line_fpos) != 0/(save_area.line_fpos = ftell(f)) == -1/" \
+    -e "s/fsetpos(input_file, &save_area.line_fpos)/fseek(input_file, save_area.line_fpos, SEEK_SET)/" reader.c
+
+# likewise, meslibc has no tmpfile()
+sed -i -e "s/tmpfile()/fopen(label, \"w+\")/" main.c
+
+# Build yacc
+make CC=tcc AR=tcc\ -ar CFLAGS=-DMAXPATHLEN=100\ -DEILSEQ=84\ -DMB_LEN_MAX=100 LDFLAGS=-lgetopt\ -static RANLIB=true
+
+# Install yacc
+install yacc ${BINDIR}
+
+cd ../..
+
+# Checksums
+if match x${UPDATE_CHECKSUMS} xTrue; then
+    sha256sum -o ${pkg}.checksums \
+        /usr/bin/yacc
+
+    install ${pkg}.checksums ${SRCDIR}
+else
+    sha256sum -c ${pkg}.checksums
+fi