decode output from compile phase

src/phases/CompilePhase.ts

@@ -17,12 +17,12 @@ export class CompilePhase extends Phase {
         Logger.verb('tsc', 'transpile sources')
         const tsc = childProcess.spawn('tsc', ['-p', this.tsconfigPath])
 
-        tsc.stdout.on('data', output => {
-            Logger.info('tsc', output)
+        tsc.stdout.on('data', (output: Buffer) => {
+            Logger.info('tsc', output.toString('utf-8'))
         })
 
-        tsc.stderr.on('data', output => {
-            Logger.info('tsc', output)
+        tsc.stderr.on('data', (output: Buffer) => {
+            Logger.info('tsc', output.toString('utf-8'))
         })
 
         return new Promise((res, rej) => {