[gnome-builder] build: be explicit about build command

[Christian Hergert <chergert src gnome org>]

commit 5304a9e20f98383b75f0184ba1d70c52471e397a
Author: Christian Hergert <chergert redhat com>
Date:   Thu Feb 21 12:34:50 2019 -0800

    build: be explicit about build command

 src/plugins/waf/waf_plugin.py | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/plugins/waf/waf_plugin.py b/src/plugins/waf/waf_plugin.py
index f4d9ab66d..12ee5d7de 100644
--- a/src/plugins/waf/waf_plugin.py
+++ b/src/plugins/waf/waf_plugin.py
@@ -98,6 +98,7 @@ class WafPipelineAddin(Ide.Object, Ide.PipelineAddin):
         build_launcher.set_cwd(srcdir)
         build_launcher.push_argv(python)
         build_launcher.push_argv('waf')
+        build_launcher.push_argv('build')
 
         clean_launcher = pipeline.create_launcher()
         clean_launcher.set_cwd(srcdir)