Execute compileall using nsExec to hide console window

Closes gh-17

nsist/template.nsi

@@ -50,7 +50,7 @@ Section "!${PRODUCT_NAME}" sec_app
   ;INSTALL_SHORTCUTS
   ; Byte-compile Python files.
   DetailPrint "Byte-compiling Python modules..."
-  ExecWait 'py -${PY_QUALIFIER} -m compileall -q "$INSTDIR\pkgs"'
+  nsExec::ExecToLog 'py -${PY_QUALIFIER} -m compileall -q "$INSTDIR\pkgs"'
   WriteUninstaller $INSTDIR\uninstall.exe
   ; Add ourselves to Add/remove programs
   WriteRegStr HKLM "Software\Microsoft\Windows\CurrentVersion\Uninstall\${PRODUCT_NAME}" \