Allow setting libc to glibc on non-glibc platform

Author: Joona Heinikoski

README.md

@@ -72,9 +72,13 @@ prebuild-install [options]
   --version                     (print prebuild-install version and exit)
 ```
 
-When `prebuild-install` is run via an `npm` script, options `--build-from-source`, `--debug`, `--download`, `--target`, `--runtime`, `--arch` and `--platform` may be passed through via arguments given to the `npm` command.
+When `prebuild-install` is run via an `npm` script, options `--build-from-source`, `--debug`, `--download`, `--target`, `--runtime`, `--arch` `--platform` and `--libc` may be passed through via arguments given to the `npm` command.
 
-Alternatively you can set environment variables `npm_config_build_from_source=true`, `npm_config_platform`, `npm_config_arch`, `npm_config_target` and `npm_config_runtime`.
+Alternatively you can set environment variables `npm_config_build_from_source=true`, `npm_config_platform`, `npm_config_arch`, `npm_config_target` `npm_config_runtime` and `npm_config_libc`.
+
+### Libc
+
+On non-glibc Linux platforms, the Libc name is appended to platform name. For example, musl-based environments are called `linuxmusl`. If `--libc=glibc` is passed as option, glibc is discarded and platform is called as just `linux`. This can be used for example to build cross-platform packages on Alpine Linux.
 
 ### Private Repositories
 

rc.js

@@ -5,7 +5,9 @@ const detectLibc = require('detect-libc')
 const napi = require('napi-build-utils')
 
 const env = process.env
-const libc = env.LIBC || (detectLibc.isNonGlibcLinuxSync() && detectLibc.familySync()) || ''
+
+const libc = env.LIBC || process.env.npm_config_libc ||
+  (detectLibc.isNonGlibcLinuxSync() && detectLibc.familySync()) || ''
 
 // Get the configuration
 module.exports = function (pkg) {
@@ -51,6 +53,8 @@ module.exports = function (pkg) {
 
   rc.abi = napi.isNapiRuntime(rc.runtime) ? rc.target : getAbi(rc.target, rc.runtime)
 
+  rc.libc = rc.libc === detectLibc.GLIBC ? '' : rc.libc
+
   return rc
 }
 

test/rc-test.js

@@ -71,7 +71,8 @@ test('npm_config_* are passed on from environment into rc', function (t) {
     npm_config_target: '1.4.0',
     npm_config_runtime: 'electron',
     npm_config_platform: 'PLATFORM',
-    npm_config_build_from_source: 'true'
+    npm_config_build_from_source: 'true',
+    npm_config_libc: 'testlibc'
   }
   runRc(t, '', env, function (rc) {
     t.equal(rc.proxy, 'http://localhost/', 'proxy is set')
@@ -81,6 +82,7 @@ test('npm_config_* are passed on from environment into rc', function (t) {
     t.equal(rc.runtime, 'electron', 'runtime is set')
     t.equal(rc.platform, 'PLATFORM', 'platform is set')
     t.equal(rc.buildFromSource, true, 'build-from-source is set')
+    t.equal(rc.libc, 'testlibc', 'libc is set')
     t.end()
   })
 })
@@ -115,6 +117,16 @@ test('using --tag-prefix will set the tag prefix', function (t) {
   })
 })
 
+test('libc glibc is passed as empty', function (t) {
+  const args = [
+    '--libc glibc'
+  ]
+  runRc(t, args.join(' '), {}, function (rc, tmp) {
+    t.equal(rc.libc, '', 'libc family')
+    t.end()
+  })
+})
+
 function runRc (t, args, env, cb) {
   const pkg = {
     name: 'test',

util.js

@@ -20,7 +20,7 @@ function getDownloadUrl (opts) {
     runtime: opts.runtime || 'node',
     platform: opts.platform,
     arch: opts.arch,
-    libc: opts.libc || process.env.LIBC || '',
+    libc: opts.libc || '',
     configuration: (opts.debug ? 'Debug' : 'Release'),
     module_name: opts.pkg.binary && opts.pkg.binary.module_name,
     tag_prefix: opts['tag-prefix']