feat: allow customization of build environment

This allows for the WASM artifacts to be built elsewhere than only in
the alpine-based node container.

build/wasm.js

@@ -9,6 +9,18 @@ const WASM_SRC = resolve(__dirname, '../deps/llhttp')
 const WASM_OUT = resolve(__dirname, '../lib/llhttp')
 const DOCKERFILE = resolve(__dirname, './Dockerfile')
 
+// These are defined by build environment
+const WASM_CC = process.env.WASM_CC || 'clang'
+let WASM_CFLAGS = process.env.WASM_CFLAGS || '--sysroot=/usr/share/wasi-sysroot -target wasm32-unknown-wasi'
+let WASM_LDFLAGS = process.env.WASM_LDFLAGS || ''
+const WASM_LDLIBS = process.env.WASM_LDLIBS || ''
+
+// These are relevant for undici and should not be overridden
+WASM_CFLAGS += ' -Ofast -fno-exceptions -fvisibility=hidden -mexec-model=reactor'
+WASM_LDFLAGS += ' -Wl,-error-limit=0 -Wl,-O3 -Wl,--lto-O3 -Wl,--strip-all'
+WASM_LDFLAGS += ' -Wl,--allow-undefined -Wl,--export-dynamic -Wl,--export-table'
+WASM_LDFLAGS += ' -Wl,--export=malloc -Wl,--export=free -Wl,--no-entry'
+
 let platform = process.env.WASM_PLATFORM
 if (!platform && process.argv[2]) {
   platform = execSync('docker info -f "{{.OSType}}/{{.Architecture}}"').toString().trim()
@@ -35,35 +47,25 @@ if (process.argv[2] === '--docker') {
   process.exit(0)
 }
 
-// Gather information about the tools used for the build
-const buildInfo = execSync('apk info -v').toString()
-if (!buildInfo.includes('wasi-sdk')) {
-  console.log('Failed to generate build environment information')
-  process.exit(-1)
+const hasApk = (function () {
+  try { execSync('command -v apk'); return true } catch (error) { return false }
+})()
+if (hasApk) {
+  // Gather information about the tools used for the build
+  const buildInfo = execSync('apk info -v').toString()
+  if (!buildInfo.includes('wasi-sdk')) {
+    console.log('Failed to generate build environment information')
+    process.exit(-1)
+  }
+  writeFileSync(join(WASM_OUT, 'wasm_build_env.txt'), buildInfo)
 }
-writeFileSync(join(WASM_OUT, 'wasm_build_env.txt'), buildInfo)
 
 // Build wasm binary
-execSync(`clang \
- --sysroot=/usr/share/wasi-sysroot \
- -target wasm32-unknown-wasi \
- -Ofast \
- -fno-exceptions \
- -fvisibility=hidden \
- -mexec-model=reactor \
- -Wl,-error-limit=0 \
- -Wl,-O3 \
- -Wl,--lto-O3 \
- -Wl,--strip-all \
- -Wl,--allow-undefined \
- -Wl,--export-dynamic \
- -Wl,--export-table \
- -Wl,--export=malloc \
- -Wl,--export=free \
- -Wl,--no-entry \
+execSync(`${WASM_CC} ${WASM_CFLAGS} ${WASM_LDFLAGS} \
  ${join(WASM_SRC, 'src')}/*.c \
  -I${join(WASM_SRC, 'include')} \
- -o ${join(WASM_OUT, 'llhttp.wasm')}`, { stdio: 'inherit' })
+ -o ${join(WASM_OUT, 'llhttp.wasm')} \
+ ${WASM_LDLIBS}`, { stdio: 'inherit' })
 
 const base64Wasm = readFileSync(join(WASM_OUT, 'llhttp.wasm')).toString('base64')
 writeFileSync(
@@ -72,27 +74,11 @@ writeFileSync(
 )
 
 // Build wasm simd binary
-execSync(`clang \
- --sysroot=/usr/share/wasi-sysroot \
- -target wasm32-unknown-wasi \
- -msimd128 \
- -Ofast \
- -fno-exceptions \
- -fvisibility=hidden \
- -mexec-model=reactor \
- -Wl,-error-limit=0 \
- -Wl,-O3 \
- -Wl,--lto-O3 \
- -Wl,--strip-all \
- -Wl,--allow-undefined \
- -Wl,--export-dynamic \
- -Wl,--export-table \
- -Wl,--export=malloc \
- -Wl,--export=free \
- -Wl,--no-entry \
+execSync(`${WASM_CC} ${WASM_CFLAGS} -msimd128 ${WASM_LDFLAGS} \
  ${join(WASM_SRC, 'src')}/*.c \
  -I${join(WASM_SRC, 'include')} \
- -o ${join(WASM_OUT, 'llhttp_simd.wasm')}`, { stdio: 'inherit' })
+ -o ${join(WASM_OUT, 'llhttp_simd.wasm')} \
+ ${WASM_LDLIBS}`, { stdio: 'inherit' })
 
 const base64WasmSimd = readFileSync(join(WASM_OUT, 'llhttp_simd.wasm')).toString('base64')
 writeFileSync(