message: feat(build.js): Add --debug flag to build Emscripten modules in debug
  When invoking the build with:
  git clean -fdx
  npm install
  npm run build -- --debug
  Emscripten modules will be built in debug mode, i.e. the JavaScript is
  not minified, and it is easier to read and debug.
diff: @@ -19,6 +19,7 @@ program
  .option('-c, --no-compile', 'Do not compile Emscripten modules')
  .option('-s, --no-copy-sources', 'Do not copy JavaScript sources')
  .option('-p, --no-build-pipelines', 'Do not build the test pipelines')
  + .option('-d, --debug', 'Create a debug build of the Emscripten modules')
  .parse(process.argv)
  if (program.compile) {
  @@ -71,7 +72,11 @@ if (program.compile) {
  } catch (err) {
  if (err.code === 'ENOENT') {
  console.log('Running CMake configuration...')
  - const cmakeCall = spawnSync(dockcross, ['cmake', '-DRapidJSON_INCLUDE_DIR=/rapidjson/include', '-DCMAKE_BUILD_TYPE=Release', '-Bbuild', '-H.', '-GNinja', '-DITK_DIR=/ITK-build', '-DBUILD_ITK_JS_IO_MODULES=ON'], {
  + let buildType = '-DCMAKE_BUILD_TYPE:STRING=Release'
  + if (program.debug) {
  + buildType = '-DCMAKE_BUILD_TYPE:STRING=Debug'
  + }
  + const cmakeCall = spawnSync(dockcross, ['cmake', '-DRapidJSON_INCLUDE_DIR=/rapidjson/include', buildType, '-Bbuild', '-H.', '-GNinja', '-DITK_DIR=/ITK-build', '-DBUILD_ITK_JS_IO_MODULES=ON'], {
  env: process.env,
  stdio: 'inherit'
  })
  @@ -209,7 +214,11 @@ if (program.copySources) {
  if (program.buildPipelines) {
  const buildPipeline = (pipelinePath) => {
  console.log('Building ' + pipelinePath + ' ...')
  - const buildPipelineCall = spawnSync(path.join(__dirname, 'src', 'itk-js-cli.js'), ['build', pipelinePath], {
  + let debugFlags = []
  + if (program.debug) {
  + debugFlags = ['-DCMAKE_BUILD_TYPE:STRING=Debug']
  + }
  + const buildPipelineCall = spawnSync(path.join(__dirname, 'src', 'itk-js-cli.js'), ['build', pipelinePath, '--'].concat(debugFlags), {
  env: process.env,
  stdio: 'inherit'
  })
  