🆕 Add build scripts

.gitignore

 node_modules/
+
+/build/

build.js

+const cli = require('webassembly/cli/util');
+const mkdirp = require('mkdirp');
+
+const srcDir = `${__dirname}/src`;
+const buildDir = `${__dirname}/build`;
+
+// CFLAGS
+const cflags = [
+  '-O3',
+  '--target=wasm32-unknown-unknown',
+  '-D', 'WEBASSEMBLY',
+  '-emit-llvm',
+  '-nostdinc',
+  '-nostdlib',
+  '-fno-builtin',
+  '-isystem', `${cli.basedir}/include`,
+  '-isystem', `${cli.basedir}/lib/musl-wasm32/include`,
+  '-isystem', `${srcDir}/include`,
+  '-I', `${srcDir}/zlib`,
+];
+
+// clang
+async function clang(input, output, cflags, cwd) {
+  await cli.run(`${cli.bindir}/clang`, [
+    input,
+    '-o', output,
+    '-c',
+    ...cflags,
+  ], { cwd });
+}
+
+// llvm-link
+async function link(input, output, linkflags, cwd) {
+  await cli.run(`${cli.bindir}/llvm-link`, [
+    input,
+    '-o', output,
+    ...linkflags,
+  ], { cwd });
+}
+
+// llc
+async function llc(input, output, llcflags, cwd) {
+  await cli.run(`${cli.bindir}/llc`, [
+    input,
+    '-o', output,
+    ...llcflags,
+  ], { cwd });
+}
+
+// s2wasm
+async function s2wasm(input, output, s2wasmflags, cwd) {
+  await cli.run(`${cli.bindir}/s2wasm`, [
+    input,
+    '-o', output,
+    ...s2wasmflags,
+  ], { cwd });
+}
+
+// wasm-opt
+async function opt(input, output, optflags, cwd) {
+  await cli.run(`${cli.bindir}/wasm-opt`, [
+    input,
+    '-o', output,
+    ...optflags,
+  ], { cwd });
+}
+
+const srcs = [
+  'zlib/adler32',
+  'zlib/compress',
+  'zlib/crc32',
+  'zlib/deflate',
+  'zlib/gzclose',
+  'zlib/gzlib',
+  'zlib/gzread',
+  'zlib/gzwrite',
+  'zlib/inflate',
+  'zlib/infback',
+  'zlib/inftrees',
+  'zlib/inffast',
+  'zlib/trees',
+  'zlib/uncompr',
+  'zlib/zutil',
+  'zlib-exports',
+];
+
+(async () => {
+  mkdirp.sync(`${buildDir}/zlib`);
+
+  // *.c -> *.bc
+  await Promise.all(
+    srcs.map(src => clang(`../src/${src}.c`, `./${src}.bc`, cflags, buildDir)),
+  );
+
+  // *.bc -> zlib.bc
+  await link([
+    ...srcs.map(src => `./${src}.bc`),
+    `${cli.basedir}/lib/webassembly.bc`,
+  ], 'zlib.bc', [
+    '-only-needed',
+  ], buildDir);
+
+  // zlib.bc -> zlib.s
+  await llc('zlib.bc', 'zlib.s', [
+    '-march=wasm32',
+    '-filetype=asm',
+    '-asm-verbose=false',
+    '-thread-model=single',
+    '-data-sections',
+    '-function-sections',
+  ], buildDir);
+
+  // zlib.s -> zlib.wat
+  await s2wasm('zlib.s', 'zlib.wat', [
+    '--import-memory',
+    '--allocate-stack', '10000',
+  ], buildDir);
+
+  // zlib.wat -> zlib.wasm
+  await opt('zlib.wat', 'zlib.wasm', [
+    '-O3',
+    '--coalesce-locals-learning',
+    '--dce',
+    '--duplicate-function-elimination',
+    '--inlining',
+    '--local-cse',
+    '--merge-blocks',
+    '--optimize-instructions',
+    '--reorder-functions',
+    '--reorder-locals',
+    '--vacuum',
+  ], buildDir);
+})();

src/import.h

+#pragma once

src/include/fcntl.h

+#pragma once
+
+#include <sys/types.h>
+
+#define O_RDONLY 0
+#define O_WRONLY 1
+#define O_CREAT  64
+#define O_TRUNC  512
+#define O_APPEND 1024
+
+int open(const char *, int, ...);
+int close(int);
+ssize_t write(int, const void *, size_t);
+ssize_t read(int, void *, size_t);

src/include/stdio.h

+#pragma once
+
+#include <stddef.h>
+
+int snprintf(char *, size_t, const char *, ...);
+int vsnprintf(char *, size_t, const char *, ...);
+int vsnprintf(char *, size_t, const char *, ...);

src/include/sys/types.h

+#pragma once
+
+typedef long ssize_t;
+typedef long long off_t;
+
+off_t lseek(int, off_t, int);

src/zlib-exports.c

+#include <stdlib.h>
+
+#include "import.h"